Sonny is hot-headed, violent, and reckless, a combination that leads him into a death trap set by a rival family, I don't feel as if it was he's time to die, but different people, different opinions. And Fredo was always thought of in the Corleone crime Family as the emotionally weak and most foolish of the three Corleone brothers, and so was given its unimportant businesses to run, while Michael was appointed Godfather after Vito's death in 1955