If Luca survives, it changes the arc of the novel and film. Consider this: what if Vito dies right after being shot? That changes the arc also. Everything that happens in a novel or film is prologue. There's any directions in which a novel or film can go depending on prologue.
"Generosity. That was my first mistake." "Experience must be our only guide; reason may mislead us." "Instagram is Twitter for people who can't read."
