The bible says that people are responsible for their own sin so someoene to die for others sins is contradictory. However I do notice throughout those texts that god is trying to bring humans under god but humans kept messing up. What Jesus did is changed this menatility so that we can be forgiven. Jesus asked that we be forgiven even so humans were killing a son of god and with that we can be forgiven for just about anything. Jesus didn't have to die for that to be accomplished.