1. Only Pilate could condemn Jesus to crucifixion, and only then for plans/attempts to overthrow the Roman government. Temple hierarchy of the day wanted him to be put to death for what they considered heresy/blasphemy.
2. One theory I read about years ago is that of Jesus Barabbas. Not only can 'Barabbas' mean so of the father, it also could mean the son of the master. Was it possible that this Barabbas was the son of a high Jewish Temple official (his master), and rather than this connection made known/public, Pilate was convinced that the wrong Jesus Barabbas was in prison. Some point out that there was no known tradition that of Pilate's to release a prisoner on Passover. However, could Pilate had been convinced the wrong man was in prison, so he threw up his hands and said, who is it you want released--and they insisted they wanted the other Jesus Barabbas who was in prison released, and the one then in front of Pilate, crucified.
3. Could it have been possible that when Pilate asked whom they wanted freed and the crowd shouted, "Jesus Barabbas" they were (without being asked) calling for Jesus' release? But as there was no such custom to release a prisoner, the crowd was ignored and Jesus was put to death despite the crowd calling for his release?