If you think about time travel seriously, you start to see how truly complicated it would make things. If the multiverse exists and time travel also exists, then inevitably there would be meddlers from the future messing things up. And following that would be those who believe such meddling is dangerous, because it creates more timelines branching off that would accelerate the meddling, until there are more polluted timelines than “natural” ones, creating a future filled with bizarrely chaotic outcomes all branching from the recursive meddling. And so there would have to be some kind of ongoing arms race of preservationists versus people who want to stack the future with timelines friendly to their own cause.