"Eyes on the prize":

Roth set it up to have the finger of suspicion point at Pentangeli. But, Michael would have asked himself, "What was in it for Frankie?" Pentangeli, by his own admission, did not have Michael's "head for the big deals." He had no eyes on Michael's gambling interests in Nevada, nor on Roth's in Havana. Despite referring to the "olive oil business" as "my family," Pentangeli was subordinate enough to Michael to come to Nevada to ask Michael's permission to whack the Rosatos. Michael would have thought that his "no" was not enough motivation for Frankie to risk everything, and become a hunted man, by killing Michael. If he wanted to defy Michael, he could have killed the Rosatos anyway--risky, but a lot less than killing Michael in Nevada. More proof: Pentangeli didn't run or hide after the shooting, and agreed with Michael's request that he "settle these differences with the Rosato brothers."

Conversely, Michael saw very soon that Roth's prize was to hold onto his Havana empire and, over time, take over the Corleones' Nevada properties through his hold on Fredo and the almost certain chaos that would follow Michael's death and the struggle for succession. As Michael said to Fredo in Havana, "He thinks he's going to live forever."