The situation reminds me of Carlo's story. As Carlo was a dead man from the moment that Sonny was killed, so whas Fredo from the moment that he revealed that he knew Roth and Ola. As he did with Carlo, Michael talked to Fredo in order to make it one hundred percent certain that he was not deceived into all this. And, of course, Michael kept them both close to him when the time was approaching . Fredo had no chance.