For what its worth, who else was there? Mary? lol Neri was an enforcer, not capable of being Don. It was a sort of pick your poison for Michael - either he had to keep being Don, or pretty much the Family was effed in the A. If there was anyone else Michael could have placed as Don, we would have seen them in GFIII, as they would have had to been high up in the family.


Vincent was nowhere near right for the job - still, he was the best man for it given the available field.