Judas was a human being and hence liable to make mistakes and sin. There are various probable explanations regarding why Judas betrayed Jesus. Some say that he as the "treasurer" of the apostles group was dipping into the till. Others that he wanted to take over the group. Whatever the case if Judas did not betray Jesus then there would be no crucifixion,and no resurrection and hence no Christianity. Everyone has a role to play in life - some positive and some negative so that we do not repeat the same mistakes. How far better are we than Judas?