There are a lot of different possible reasons for the betrayal, and it doesn't matter which one you think is closest to the real reason because they all come to the same thing. Judas suffered from the exact problems we still see in people today: they will believe whatever they want to believe, regardless of what makes sense, the truth, or the consequences. Judas was not interested in the truth or seeing God's plan fulfilled. He only wanted to push his own agenda. How many times do we see this carried out every single day in politics and society? Some people do all sorts of evil things to win and rationalize it.