From the time Vito is shot the time he comes home from the hospital, Fredo is kept out of the loop as to what is going on with the mob war. He isnt in the room when Michael comes up with the plan to shoot Sollozzo and McCluskey, he isnt there while they are waiting around to find out where Sollozzo is taking Michael for dinner, and he isn't even there to say goodbye to Michael. Obviously both Sonny and Tom knew he was pretty worthless, but I wonder if even then they completely trusted him even then.
After Don Vito was shot down, Fredo was in shock and out of the picture until he recouped. If you remember, Fredo had as much a hand in the Family Business as Santino and even Tom - Fredo was in the initial meeting at Genco with Sollozzo, along with the
Caporegimes Clemenza and Tessio, Santino, Vito, and Tom. You didn't see
Michael there.
Up until the time of Vito's shooting, Fredo was right there.
