The John Cazale Fredo is very strong dramatically. It's completely dissonant from the Fredo of the book, though. He's a Mafia member in good standing, both Sonny and Michael remark on his toughness. What he lacks I think Puzo calls "personal force." He collapses because his ego requires Vito's approval, while Sonny and Michael (and Connie?) don't need that.

It been said that the sons represent the parts of human nature: Sonny is ruled by emotion or passion, Michael by intellect, and Fredo by the physical. I think that's why Puzo threw the cooking thing in there, to show that's Fredo's key is the satisfaction of his physical needs.