I think you might be letting Fredo in the movie bleed into Fredo in the book. I think the novel might describe him as "dutiful," maybe not the sharpest cookie but mostly just lacking in imagination and drive. I think that when he falls apart after the shooting, they say they were surprised because he was a genuinely tough guy.
Thanks for the explanation mustachepete. You're right. I've never been able to finish the novel and don't remember much about what I did read.
I was thinking about his portrayal in the movie.
