This happened so that the words Jesus had spoken indicating the kind of death he was going to die would be fulfilled.
The charge which the Sanhedrin had against Jesus is not a Roman violation, but a Jewish one: blasphemy (Mark 14:64) which had a penalty of death by stoning (Lev 24:16). Jesus had already escaped stoning on at least 2 previous occasions (John 8:59, 10:31) and had predicted the form of His death as being crucifixion (John 3:14, 8:28, 12:32-34; Matt 26:2) which will now be fulfilled. Jesus had also predicted that He would be handed over to the gentiles to be put to death (Mt 20:19; Mark 10:33; Luke 18:32-33). It is indeed interesting that they who were trying to kill the sayings and teachings of Jesus, were instead instruments in the hand of God to bring about their fulfillment!
Mark 14:64 “You have heard the blasphemy. What do you think?” They all condemned him as worthy of death.
Leviticus 24:16 anyone who blasphemes the name of the LORD must be put to death. The entire assembly must stone him. Whether an alien or native-born, when he blasphemes the Name, he must be put to death.
John 8:59 At this, they picked up stones to stone him, but Jesus hid himself, slipping away from the temple grounds.
John 10:31 Again the Jews picked up stones to stone him,
John 3:14 Just as Moses lifted up the snake in the desert, so the Son of Man must be lifted up,
John 8:28 So Jesus said, “When you have lifted up the Son of Man, then you will know that I am the one I claim to be and that I do nothing on my own but speak just what the Father has taught me.
John 12:32-34 But I, when I am lifted up from the earth, will draw all men to myself.” He said this to show the kind of death he was going to die. The crowd spoke up, “We have heard from the Law that the Christ will remain for ever, so how can you say, ‘The Son of Man must be lifted up’? Who is this ‘Son of Man’?”
Matthew 26:2 “As you know, the Passover is two days away—and the Son of Man will be handed over to be crucified.”
Matthew 20:19 and will turn him over to the Gentiles to be mocked and flogged and crucified. On the third day he will be raised to life!”
Mark 10:33 “We are going up to Jerusalem,” he said, “and the Son of Man will be betrayed to the chief priests and teachers of the law. They will condemn him to death and will hand him over to the Gentiles,
Luke 18:32-33 He will be turned over to the Gentiles. They will mock him, insult him, spit on him, flog him and kill him. On the third day he will rise again.”
It is thought by many that Caiaphas did not want Jesus to die by stoning but by crucifixion because in that way there would be a curse attached to Jesus (Deut 21:22-23) and every Jew would see that Jesus could not possibly be the Blessed One of God because He was a cursed blasphemer. However, Caiaphas missed the point that God wanted Jesus to be cursed so that He would take our curse from us (Gal 3:13).
Deuteronomy 21:22-23 If a man guilty of a capital offence is put to death and his body is hung on a tree, you must not leave his body on the tree overnight. Be sure to bury him that same day, because anyone who is hung on a tree is under God’s curse. You must not desecrate the land the LORD your God is giving you as an inheritance.
Galatians 3:13 Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: “Cursed is everyone who is hung on a tree.”