And well a bunch of the streamer boom is gone too, I'm sure a lot of people who tried playing the game quit because they didn't like it, or already cleared out the story, or are taking a break before the expansion or trying New World and so on. I wouldn't make a char there if you want to play Endwalker though, cause that shit will be crowded once some of these people return.
Honestly with the big popularity boost combined with the server shortage issues, I'm not too confident about Endwalker launch overall. Shadowbringers was basically perfect(I think a couple of DCs rebooted or some shit, and there were queues, but I know I had basically no issues on the EU Chaos DC) but I'm a bit scared this might turn more into a repeat of Stormblood with instance servers crashing/being full and shit. Partly why I'm gonna avoid the new classes and try to get as far as possible through the story first, so if there's issues with instances I can at least hop on other classes and just grind fates and shit.