Maybe I am missing the point but I thought
He was doing it because of unbelief.
Rather than by agreement, seems the reaction would be different
Oh, okay. I interpreted your comment as ‘why do people commit sucide?’
As for his suicide, he hung himself (Matthew 27:5) and then bought some land whereof to fall down and explode (Acts 1:18). Since there are no biblical contradictions, one can only be awestruck at his creative determination. His mission complete, he wanted to die at his own hand, rather than miss the spectacle he had in mind. ;}