Because the scripture cannot lie, Jesus was to be crucified and because of that, Barabbas was to be released and Jesus flogged and released to the people.

Because they thought Jesus was blaspheming, they did not believe He was the son of God and the elders thought He was a treat to them.

Jesus was going to be crucified wether it was Judas or someone else, but the bible did not tell us that it was going to be Judas who will betray Jesus.

It was wrong because it was one of His own deciple whom he has thought the way and who has been with Him and see Him perform miracles.

It was wrong for Judas because he did it with a bad intent to get the money and thought that well Jesus is God, He can serve Himself. He did it because of greed and not the fact that the bible says Jesus will be crucified or that he, Judas wants to be part of the redeem of man and there was no other part to play but the betrayer.