The Barzini family was so close to succes by using Michael's trusted bodyguard, Fabrizio to planted the bomb in Michael's car. So what if Michael got killed along with his wife in the car. And Sonny got massacred. The only left is Fredo....lol.

So, Vito is retired so who would Vito passes his role of head of the family to?

Vito made the peace knowing an attempt was going to be made on Michael.

Sonny was already dead. Vito made a deal knowing that he could try to neutralize the threat against Mike. knowing that Mike would take revenge after he was out. As Vito said, if Mike dies then he is going to blame some of the people in this room.
Vito made the peace and seemed to be weak, knowing that once he was out Mike would handle things that needed handling.
Revenge on Tattaglia, Barzini, and Carlo

Once Mike is killed Vito does all of those things himself with Clemenza and Tessio

Vito got out of his sick bed and ran the family again as soon as he learned that Sonny was killed. That was before the bomb attempt on Michael. Had Michael been killed, Vito would have continued to run the family. He probably would have asked for a truce anyway, to buy time. He would have groomed Clemenza and/or Tessio to take over for him. Fredo would have stayed in Vegas.

What about Tom taking over, like he eventually did. Vito could have made the others agree to that also if he wanted.

Loyalty and trust is proven by actions, not blood or tradition, Michael learned and knew that from his Father and brother.

If Mike was killed in the car bombing in Sicily then "The Godfather" would have been a short story instead of a novel. The whole premise of the story is the son taking over his father's business.

Tom was agreeably every much of a Son as all of them.

Exactly SC. Otherwise, the film would have been an egregious departure from the novel.

Oh come on. We all know Connie would have taken over.

Come to think of it, didn't she sanction the Joey Zasa hit?

Then just hand the whole thing over to Merle.

Would he and Fredo have a slappy fight for the Don's chair?

With that being said, I must agree....

Connie runs the Family.

Seems like a reasonable course of action. My guess is that it would never happen. While Tom was an able lawyer and competent businessman, Tom wasn't from the muscle end of the family, and he wasn't Sicilian.

When push comes to shove (the LCN business model), he didn't have the necessary killer instinct to succeed as the don in such a cutthroat enterprise. And his German-Irish ethnicity would, at least at that time, have always been looked upon with suspicion by the Sicilians, making it difficult for Tom to operate freely.

~ Q