Earlier quoted context omitted.
There was social media before Facebook, though.
I think if social media is WW1, then the launch of Facebook will be considered as the assassination of Archduke Franz Ferdinand. Not in itself sufficient, but a point that really got some important balls rolling.
The revolutionary change that made Facebook uniquely successful wasn't being a social media platform, it was forcing its users (who were so far treating it as a way to keep in touch with acquaintances, old friends and distant family) to compete for each other's attention and offering corporations the opportunity to join that competition - all the while retaining the messaging that the platform is about "social" interactions between peers. And of course mining the everliving #### out of their users' data while non-consensually tracking them across the entire web without their knowledge.
But the "attention is the currency in the marketplace of ideas" concept they launched pretty much defined all "social media" companies from that point on, which is why we nowadays often forget the term used to be much more appropriate in the past (although often constrained to a crowd of very technical nerds).
Oh, and of course they very successfully killed much of the tradition of the Open Web by encouraging a walled garden approach even when it required them to actively defraud their advertisers by lying about the performance of video content. But I think the trophy for launching that extinction event belongs to Apple when they pivoted away from the original web-first concept for the iPhone to the proprietary App Store.