Vito saw that move coming from a mile away. He even told Michael specifically how it was going to go down. So that raises the question of who Vito was really concerned about coming after Michael. Was he preparing him for Barzini's next move or did he foresee one of his two top men betraying the family.
Maybe Vito saw it from a mile away, but he wasn't a psychic. He couldn't foresee every move. It was clear, it had to be someone close to Michael - Tessio, Clemenza, Rocco, Al Neri, Carlo, Tom, Fredo. Their were advantages and disadvantages by approaching each of these men. I'm not sure whether it was Tessio who approached Barzini. Barzini wouldn't wait too long, he wanted to get rid of Michael as soon as possible.
Still, it was dangerous to approach Tessio, just as dangerous as it was for Brazi to approach Bruno Tattaglia.
Everyone of the guys mentioned above - except perhaps for Neri and Rocco - had their reason to be unhappy with Michael.
- Neri was simply
too close to Michael.
- Rocco was the security guy (as I understand it).
- Approaching Carlo would be the most stupid move. Everybody would have smelled the rat immediately.
- Fredo had been humiliated by Michael and by his father, but maybe too far away. Roth later realized that approaching Fredo was the smartest move one could do.
- Tom had been dismissed as consigliere. I wonder if Barzini could have considered him.
- But Tessio and Clemenza suffered immediateley from the "Keep your hands still"-tactics of Michael. So it had to be one of them.
