
Question: During the crucifixion of Jesus Christ, how did 1 of the 2 thieves come to change his mind from unbelief to belief and believe the Gospel of Christ while the other did not come to belief during the scriptural account of their crucifixion ?

The chief priests, the scribes, the elders, who were the traditional religious people of Jesus’ day, the 2 plunderers being crucified with Jesus Christ, one on the right and one on the left of Jesus and those passing by were all either mocking, reviling and or blaspheming Jesus and His Gospel. They told Him to come down from the cross and save himself like He saved others.
“And also the plunderers (plural)crucified with Him defamed Him, saying the same.”
“He saved others”
“He is not able to save himself “
“Let come down The Christ”
“The King of Israel”
“You the one razing the temple and building it in 3 days”
“Save yourself”
“Come down from the cross”
“He trusted God Let him rescue him now”
“If he desires him”
“For He said, I am Son of God.”
“If you are the Son of God come down from the cross”
“But those passing by blasphemed Him, shaking their heads”
The following verses give us reasons why they all were mocking and did not believe.
1 Corinthians 2:14,15
But a natural man does not receive the things of the Spirit of God, for they are foolishness to him, and he is not able to know them, because they are spiritually discerned.
15 But the spiritual one discerns all things, but he is discerned by no one.
Romans 3:10-12
according as it is written, “There is not a righteous (one), not even (one)”
There is not (one) understanding, there is not one seeking God”
All turned aside; together (they) became worthless, not (one) (is) doing goodness, not so much as one!”
Romans 3:19-26
But we know that as many (things) as law says, it says to the (ones) within the law, so every that mouth may be stopped, and all the world be accountable to God.
Because by works of law not one of all flesh will be justified before Him, for through law (is) full knowledge of sin.
But now apart from law a righteousness of God has been revealed, being witnessed by the Law and the Prophets.
even the righteousness of God through the faith of Jesus Christ toward all and upon all the (ones) believing, for there is no difference,
for all sinned and fall short of the glory of God,
being justified undeservedly by His grace through the redemption in Christ Jesus,
whom God set forth (as) a propitiation through the faith in His blood, for a demonstration of His righteousness through the passing over of the sins that had taken place before, in the forbearance of God,
for a demonstration of His righteousness in the present time, for His being a just (One) and justifying the (one) that (is) of the faith of Jesus.
1 Corinthians 1:18
For the Word of the cross is foolishness to the (ones) perishing but to us being saved it is (the) power of God.
1 Corinthians 2:8–11
8 which none of the rulers of this age has known. For if they had known, they would not have crucified the Lord of glory;
9 but even as it is written, “The things which an eye did not see, and an ear did not hear,” and did not come up on the heart of man, the things which God has prepared for the ones loving Him.
10 But God revealed them to us through His Spirit, for the Spirit searches all things, even the depths of God.
11 For who among men knows the things of a man, except the spirit of a man within
The following verses reveal how a person comes to the knowledge of the truth of The Gospel of Jesus Christ
Matthew 11:27
All things were given over to Me by My Father; and no one knows the Son except the Father; nor does anyone know the Father; except the Son, and to whomever the Son purposes to reveal (Him)
Matthew 16:15-18
15 He said to them, But you, whom do you say Me to be?
16 And answering Simon Peter said, You are the Christ, the Son of the living God
17 And answering, Jesus said to Him, Blessed are you, Simon, son of Jonah, for flesh and blood did not reveal (it) to you, but My Father in heaven
18 And I also say to you that you are Peter, and on this rock I will build My Assembly and (the) gates of Hades will not prevail against her.
John 6:37 (Read verses 38-44, 29, 65)
All who the Father gives to Me shall come to Me, and the (one) coming to Me I will not cast out, not ever.
2 Corinthians 4:6
Because (it is) God who said, “Out of darkness Light shall shine” the (One) who shone in our hearts to (give) illumination of the knowledge of the glory of God in the face of Jesus Christ
The Gospel that all believe once God shines into the heart the illumination of the knowledge of the glory of God in the face of Jesus Christ is: God promises to save His people (chosen unconditionally according to His will and purpose from before the foundation of the world ) conditioned solely on the atoning shed blood of Jesus Christ and His imputed righteousness without any effort, contribution and or work from those for whom He died. Romans 9:11 Ephesians 1:4 Romans 3:9-31 Romans 4:3-8 Matthew 1:21
Salvation is based on the work and person of Jesus Christ alone from regeneration to final glorification when He comes again to change the corruptible into incorruptible; doing away with sin and death. 1 Corinthians 15, John 3:3,5,8 Hebrews 9:28 Hebrews 9:22 Revelation 20:14
The following verses from 3 Gospels, Matthew, Mark and Luke give account of what happened during the crucifixions
Mark 15:26-39
26 And the inscription of His accusation was written over (Him), THE KING OF THE JEWS.
27 And they crucified two plunderers with Him, one at (the) right, and one at (the) left of Him.
28. And the scripture was fulfilled which says”And He was numbered with (the) lawless” Isaiah 53:12
29 And those passing by blasphemed Him, shaking their heads, and saying, Aha! (You) razing the temple, and in three days building (it)
30 save Yourself and come down from the cross.
31 And also the chief priests and the scribes mocking to one another said likewise, He saved others; He is not able to save himself
32 Let come down the Christ, the king of Israel now come down from the cross, that we may see and believe Him. And the ones crucified with Him were reviling Him.
33 And (it) being (the) sixth hour, darkness came over all the land until the ninth hour
34 And at the ninth hour Jesus cried with a loud voice, saying, Eloi, Eloi, lama sabachthani? (Which being translated is My God, My God, why did you forsake Me?)
35. And hearing, some of those standing by said, Behold, He calls Elijah.
36 And one running up, and filling a sponge with vinegar, and putting (it) on a reed, was giving Him to drink, saying, Leave alone, let us see if Elijah comes to take Him down.
37 And letting out a cry, Jesus breathed out (His) spirit.
38 And the veil of the temple was torn into two, from top to bottom.
39 And the centurion standing near across from Him, seeing that crying out so He breathed out (His) spirit, (he) said, Truly, this Man was Son of God.
Matthew 27:38-44 (KJ3 literal)
38 Then two plunderers were crucified with Him, one on the right, and one on the left of Him.
39 But those passing by blasphemed Him, shaking their heads,
40 and saying, You the One razing the temple and building it in three days, save Yourself. If You are the Son of God, come down from the cross.
41 And in the same way, the chief priests with the scribes and elders, mocking, said,
42 He saved others; He is not able to save Himself. If He is the King of Israel, let Him come down now from the cross, and we will believe Him.
43 He trusted on God. Let Him rescue Him now, if He desires Him. For He said, I am Son of God.
44 And also the plunderers crucified with Him defamed Him, saying the same.
Luke 23:33
And when they came on the place being called Skull, there they crucified Him and the criminals, one at (the) right, and one at (the) left.
Luke 23:34
And Jesus said, Father, forgive them, for they do not know what they are doing. And dividing His garments, they cast a lot.
Jesus knew that the Father chooses and The Son redeems and The Spirit regenerates those that the Father gives to Jesus; who will come to Jesus believing into His work and person as the only grounds of their salvation. They will show their love by striving to keep His commandments. John 6:37-44 John 3:3,5,8 Romans 1:16-17 Romans 3 Romans 4 John 14:15 John 6:65 John 10 Ephesians 1:7
Luke 23:39
And one of the hanged criminals blasphemed Him, saying, If You are the Christ, save Yourself and us.
40 But answering, the other rebuked him, saying, Do you not fear God, for you are in the same judgment?
41 And we indeed justly, for we receive things worthy of what we did. But this One did nothing a miss.
42 And he said to Jesus, Lord, remember me when You come in Your kingdom.
43 And Jesus said to him, Truly I say to you, Today you will be with Me in Paradise.
44 ¶ And it was about the sixth hour, and darkness came to be over all the land until the ninth hour.
45 And the sun was darkened, and the veil of the temple was torn apart in the middle.
46 And crying with a loud voice, Jesus said, Father, “into Your hands I commit My spirit.”And saying this, He expired.
The following is a biblical analysis of the change of heart of 1 of the 2 plunderers.
We know from the scriptures above that both plunderers started out defaming, mocking and reviling Jesus and His Gospel.
We know from the scriptures above 1 Corinthians 2:14-15 and 1 Corinthians 2:8-11, Matthew 11:27 and 2 Corinthians 4:6 that God through generation from above is responsible for causing the change from being dead spiritually to being spiritually alive unto belief of the Gospel of Christ please also reference John 3:3,5,8 Ephesians 2:5
We know that one of the plunderers went from defaming, reviling and mocking Jesus to calling Him “Lord”
Why did this particular plunderer have a change of heart towards the truth and the other plunderer had no change of mind?
God must have shined into his heart the illumination of the knowledge of the glory of God in the face of Jesus Christ; His being Lord of all creation, His work and His person. 2 Corinthians 4:6
We can deduct that the changed plunderer knew that both he and Jesus were going to physically die that day.
But even though he knew they would physically die that day, he still said to Jesus “Lord, remember me when You come in Your kingdom.”
This tells me the plunderer knew Jesus was Lord of all creation and that His salvation rested in His mercying whomever He chooses to mercy. Romans 9:15,18 Luke 18:13 The plunderer knew his unrighteousness and he submitted to the righteousness of God through the work and person of Jesus Christ after God shined into his heart the illumination of the knowledge of the glory of God in the face of Jesus Christ Romans 10:1-4 Romans 3 and Romans 4
There is no way an unconverted natural fallen man, a descendant of Adam, would make the statements he made and would have understood the spiritual things that he understood unless God had made him alive through the gift of the spirit supplying a new heart and a new spirit unto belief of the Gospel of Christ Ezekiel 36:26 John 6:29
This account of the converted plunderer by God is a perfect and vividly portrayed example of salvation by the Grace of God alone through the atoning shed blood and imputed righteousness of Jesus Christ alone without any effort or work from the people He promised to save; chosen unconditionally from before the foundation of the world; Ephesians 1:4 Matthew1:21 the ones for whom He vicariously substituted and promised to save. Revelation 7:9
John 14:6
Jesus says to him, I am the Way, and the Truth, and the Life. No one comes to the Father if not through Me.
John 6:44
No one is able to come to Me if not the Father, the ( One) having sent Me, draws ( drags) him, and I will raise him up in the last day
Man’s nature acquired from Adam’s fall in the Garden of Eden, left his descendants with a hard spiritually dead heart towards the true God; causing them to run away from The True God.
A metaphorical term “drag” was used above to describe what it would take considering man’s sinful nature, being a natural man, to come believing on his own into Jesus’ work and person alone as the only condition for salvation; but considering God’s power and Grace, it only requires a drawing on God’s part which requires little effort on God’s part to cause a person to come willingly.
God causes a shining into the heart the illumination of the knowledge of the glory of God in the face of Jesus Christ and they pass from death to life and they come believing into the only Savior of the World. Psalm 33:16 2 Corinthians 4:6 John 5:24
The converted plunderer received from God the shining into his heart the illumination of the knowledge of the glory of God in the face of Jesus Christ and passed from death to life.
John 5:24
Truly, truly, I say to you, The (one) who hears My Word, and believing the (One) having sent Me, has everlasting life, and does not come into judgement, but has passed out of death into life

Highlights and italics added for emphasis and focus.
Scripture taken from KJ3 literal translation