Dead men make no policy
Absolutely his demise would invoke conspiracy theories at least on the level of JFK, even without an assassination. But he is the shepherd, and the sheep will follow no other like they do him. Certainly there will be others who will try to lead the MAGA insane, but most of the GOP will slowly morph back into their old asshole selves. And I'm postive most GOP leaders would breathe a sigh of relief to see the orange cancer no longer in this world.