Had Michael been killed in Sicily, Vito, weakened by the shooting and devastated by the loss of two sons, still would have had Tess and Clem's loyalties, as well as their formidable regimes. He also would have retained his even more formidable police/political contacts, which the other families needed:
To them, Vito was a beaten man, but they needed his police/political protection. That would give Vito time to think, to plan, to remain the head of the family for several years, as we saw..
As he approached his death, and with Barzini chiseling Corleone territories, I believe he would have counseled Tess and Clem to make their peace with Barzini and go with him, since he would be gone and Fredo couldn't lead them. They might not go for it, but that would be their problem.
Would beaten and weakened Vito still retain his police/political contacts?
You see -- all these people are business men, their loyalty is based on that
If Michael had been killed in the car bomb, would Barzini still chisel Corleone territories?
Tess and Clem hate that goddamn Barzini! can't see them operating under Barzini's thumb
He also would have been suspicious it was a plot by Vito (a la Luca/Tattaglia) to suss out Barz's intentions
plus it would disrupt Vito's plans to gradually get out of the crime "business" and retire peacefully.
Don't know Lou He left the legitimacy burden for Michael
I work my whole life, I don't apologize, to take care of my family. And I refused -- to be a fool -- dancing on the string, held by all those -- bigshots. I don't apologize -- that's my life --
