This could be said of many who played a part in the Crucifixion, but didn’t they all have to “do their part” in order that he be crucified to redeem us? I’ve been trying to figure this out for years. If it had to be, are these people culpable? How does it all work?
Yes, those who took part in Christ’s Crucifixion had to “do their part” in order for the Crucifixion to take place. In other words, yes, they had to choose to take part in the Crucifixion. And yes, they are culpable for the sins they committed by condemning and putting to death an innocent man. (That man was God, which materially worsened the crime, but there is no hint that Christ’s executioners understood that they were putting God to death. Christ prayed “Father, forgive them; for they know not what they do” Luke 23:34].)
If the Crucifixion was ordained for our redemption, how could those who took part in the actual event be culpable? Because God used their sins to bring about the greater good of the forgiveness of their sins and the sins of all mankind. As he is God, he knew what the people of his time would choose to do. That doesn’t excuse their sins, any more than God’s foreknowledge of our future sins will excuse us from choosing to commit those sins. In Pilate’s case, Jesus expressly said that Pilate sinned in his actions although Jesus’ betrayer Judas had the greater sin (cf. John 19:11).