Yeah yeah, I know, Duvall wanted too much money so he was not in III and there was a plot device by which we are led to think he died of natural causes, and that his widow and son were at the party.

BUT isn't it possible that Michael had Neri give Tom something to induce a heart attack or whatever? My reasoning is that between the end of II and the beginning of III, Michael was on his bizarre quest to become "legitimate." After the end of II the ONLY person other than Mike who were
originally with Mike were dead. All of Vito's top people and even middlemen were dead. In other words the only person with an institutional memory of Everyithing was Tom, who BTW appeared on that Senate chart as a member of the "family." Michael wanted all traces of his Vegas dealings to be in the past when he moved to New York. He sold all the casinos, abandoned his house in Tahoe, and along the way Tom's lips are sealed forever. Coincidental heart attack? Maybe not.