First, there are countries where Facebook is de facto synonym for the Internet. Thanks to its marketplaces, groups, and events, there are places where much of the online economy is heavily based on Facebook.
Second, I'd argue that nearly every mobile provider in the world that offers zero-rating does so by providing access to Facebook's services either free of charge or at a much lower price than the rest of the Web.
Absolutely no other company in history had these two advantages over not just their social media competition, but the rest of the Web as a whole.
By any reasonable measure, that was "at the same time"; it wasn't so much one replacing the other replacing the next as three early competitors fluctuating until one won out.
None of those browsers ever came near the global reach of IE. A quick Yahoo search gives a peak user count of Netscape of around 80 million, for IE it's around 800 million.
Not that I believe for one second Facebook has 2.7 billion active individual human users. I've never even used it but I've signed up to about 10 accounts over the years, and everybody I know also has multiple accounts for various reasons.
In fact based just on people I know, I wouldn't be surprised if already most people are just using "Facebook" for messenger.
Plus, I think society as a whole is beginning to see the toxic ills of social media in general and will push back in a "retro" "back to the basics" kind of movement, embracing old traditions like community, family and friends in meatspace.
I honestly laugh whenever I hear people still bring up those early social media companies as evidence that social media heavyweights somehow come and go. None of those companies ever came near the global reach of FB. A quick Google search gives a peak user count of MySpace of between 75 and 100 million, for FB it's 2.7 billion.
Those companies basically all existed before the vast majority of people were even on any social network, and importantly none of them had real-name policies initially. And the modern challengers you give all have some specific, much smaller niche, e.g. image galleries for Pinterest. There is simply no other social network that has ever challenged Facebook in the "connect all my friends and let me give and see life's updates" space.