I agree with Lilo: it was Michael the perpetual controller being true to his character. Notice that he didn't give Vincent full rein until after Don Tomassino was killed. Only then did he realize that he was aging, infirm and vulnerable--and had to put someone younger, more ruthless, in charge.

One think intrigues me in the scene you cited, Vito. Michael spits out, "That is not...what I...WANTED!." Well, what did he want? Just before he had his diabetic stroke, he seemed to be cooking up a Vito Corleone-type submissive charade ("Get a message to Zasa...I respect what he did...[the old order changeth])..." In the same scene he said, "Our true enemy has yet to show himself." My guess is that, at that instant, he might have been planning to get closer to Zasa to learn who his true enemy was--just as Vito learned after the Don's Convention that it was Barzini all along.

But then, during the stroke, he seems to realize it was Altobello all along. So, he no longer needed Zasa to lead him to the unknown true enemy.

Ok, Vincent et al violated his almighty control obsession by ordering Zasa's assassination. That explains "never give an order like that..." But it still doesn't reveal what Michael "wanted," having realized that Altobello was the enemy.