When Michael tells Carlo he will be his right hand man after their move to Nevada, Carlo before he leaves, thanks Vito and Vito responds with an affectionate “I’m happy for you, Carlo”

Had Michael and Vito already worked out Carlo’s role in Sonny’s death? More so, did Vito know before Michael or because of his continued case of slipping, had it not dawned on him yet?

I think the family knew immediately that it was a setup, and that Carlo had to be involved in it because only he could make Connie call Sonny for help. There's a passage in the novel, even before Tom tells Vito, where Tom calls Carlo and reassures him that no one will blame him, but Tom's really just pinning Carlo down so the family can deal with him on their own schedule.

Pete's right. Vito and Tom knew right away that Carlo had set up Sonny. It's been speculated here that Vito simply couldn't bring himself to have his daughter's husband killed, especially in the state of grief and shock he was in because of Sonny's death. Also, as Vito states in the novel, "Revenge is a dish best served cold." Vito and Michael were jollying Carlo along until the time was ripe--after Vito died and on the day when Michael "settled all family business."

Carlo exemplifies how greed and lust for revenge blind people--a regular theme in both the novel and the movie. How the hell could Carlo think he could get away with anything so obvious as that setup?

Ah yes, of course.

It's been a long time since I've read the source material

Thanks guys

Vito always the 'nice' guy!

Vito planned all the dirty work - killing of Carlo Rizzi [for Michael to make his daughter a widow] and Moe Greene, the baptism murders - for Michael to carry out after Vito's death thus leaving a murderous legacy for “I never wanted this for you” son

In the film, as Carlo is leaving Vito's office, Vito shows Carlo affection and tells him that he is happy for him. How insidious! If it's cold revenge, how cold, indeed! For some film viewers, Vito gets a pass because they view him as a hero of sorts fighting valiantly against the deadly intrigues of Barzini and the five families. But that ignores the evil Vito. Carlo was a protagonist in Sonny's death. Therefore, like any father, Vito sought payback. That was not a stretch for him; payback was part and parcel of who Vito was.

Right, Oli. And Michael tells you, right at the beginning of the book. Kay's lapping up his funny stories, and he tells her, "I guess that’s the way it sounds, but let me tell you this. You know those Arctic explorers who leave caches of food scattered on the route to the North Pole? Just in case they may need them someday? That’s my father’s favors. Someday he’ll be at each one of those people’s houses, and they better come across."

Vito is seen through rose-coloured glasses He was a cold blooded murderer despite his outward nice guy appearances, committing horrendous acts, cold blooded gruesome murders, destroying families / businesses including his threat of lethal force for the release of his Godson's contract shows where Michael got his cold bloodedness

Both were evil, ruthless, murderous crime boss Like father like son The difference was their wives