I think it's better to understand "fate" as a natural phenomenon. It's not that it "wants" someone to die, it just has to happen. If you are really interested "Steins; Gate" is a 24 episode anime with a huge emphasis on this concept. Similar timelines will wield similar results and, while possible, it's very difficult to move to a timeline that will bypass that. The special someone had access to memories of many past iterations and likely came to the conclusion that someone has to die because it always happens. The vault not working earlier because it goes to it's very principle that of unlocking past iterations memories, if something hasn't happened before it's just not going to work. Eventually it reaches a point that it has accumulated enough information that it can work "earlier". As for the "butterfly effect" that theory for time travel is more popular, but it's opposite to the convergence theory on how it functions, i doubt it'd be possible to have both in the same story.