I don't know here. I'm 50 / 50 on this. After Mike "forgives" Fredo at his mother's wake, Fredo seems at ease (which was Mike's intent of course). Part of me believes that Fredo felt that Mike was sincere in forgiving him, and that he was finaly off the hook. At that point I don't know if Fredo would have taken another opportunity to go against Mike, or do something behind his back again. I think that Fredo realized that he was duped the first time, and was too scared to ever let himself get duped again into doing something behind Mike's back.

And in my thinking this way, the question is, did Fredo intentionally set up Mike, or did he really think that he was just spiting Mike and getting even with him by trying to make a deal on his own?. Personally I think that he was fooled by Ola and Roth. I don't believe that he ever intended to have Mike physically hurt. His dealing with Ola was more out of anger of being passed over and he thought that it was his chance to finally show Mike that he was smart and could do things on his own. I don't think that there was ever a intent on Fedo's part to physically hurt Mike or help have him killed. Fedo had too much of a heart to go that far. And that is why I think that Fredo learned his lesson and would never make that mistake again concerning Michael's well being.

Michael was a son of a bitch to have Fredo killed.