Likewise, since Rip did not know about the Occulus, he assumed that events were happening a certain way because of an almost mystical "Time wanting it to happen" explanation but then we learn the truth that Time was simply being manipulating by the Time Masters.
Except it's not mystical at all, really. It makes sense that history would resist change. Any event is the result of thousands of converging factors that lead up to it, and there are few instances where changing just one thing will divert the overall flow of history. For instance, if you went back in time and killed Hitler, there'd probably just have been someone else who would've taken his place and done much the same things. Because Hitler didn't make Nazi Germany happen singlehandedly; he just provided a focus for the widespread anger and dysfunction that already existed among the people. And he himself was a product of his upbringing and environment, so there were probably numerous others much like him in that same place and time. It would probably take a lot more interventions going back much further in time to undo the entire chain of circumstances that led to WWII and the Holocaust. Or else it would take a particularly massive change to alter things in one go, like, say, giving England nuclear weapons in 1917. (And yes, I'm sure one could nitpick the specifics of these examples, and they're probably far from perfect, but I'm just using them to illustrate the idea, so let's try not to get into that.)
It also makes sense dramatically for a time-travel series, which is why the same basic assumption is used on many such shows, including
FlashForward, Terminator: The Sarah Connor Chronicles, Continuum, and
12 Monkeys. On the one hand, you want it to be at least possible to change history, or there's no point to the heroes' quest at all; but on the other hand, you want it to be really hard, because if the heroes could do it easily, you couldn't sustain the show for multiple seasons. So the ideal approach for a time-travel series is exactly the one this show is using, that history resists major changes unless you manage to change just the right thing(s) in just the right way. "Time wants to happen" is just a poetic way of expressing that principle.