Poul Anderson [1] in its short stories Time Patrol has this theory that the past can be disturbed to some extend, some things have to happen independently of particular individuals or events.

As a let down as it is for readers interested in how the author handles and solves time paradoxes (it is better than the insipid and sloppy multiverse solution, though) - Time Patrol are mostly history-focused action stories - this theory makes sense to me. At some point the world gets "ready" to discover things because all the pieces of the puzzle are in its hands. In the case of Facebook, I believe it is not an accident or "because Zuckerberg"; a massive social network had to emerge, in particular due to network effects.

[1] https://en.wikipedia.org/wiki/Poul_Anderson