They might have been declining since then, but more recently I'd point to when they introduced Dr. Who, Transformers, My Little Pony, and a whole bunch of other crap into a game about wizards fighting in a fantasy world.
In the short term all the franchises have proved incredibly popular (just like in Fortnight), but in the long run I think it means the death of the game (just like where Fortnight is headed).
It is both true that there has been an OSR revival, and that D&D is more popular than ever -- just with a much broader and culturally normative audience.
Also: Yes, Hasbro did some shit, but they also had to relent and CC their SRD. This all happened years ago.
I say this as a committed Pathfinder player who hasn't seen a good reason to return to D&D (PF2e is good enough). D&D is doing numbers and no one cares that us nerds moved on because of weak tea from the previous decade.
D&D had a massive player revolt a while back in response to WOTC (at the requirement of Hasbro) trying to take ownership over everything players create in the D&D universe, breaking their long-standing promise to all of those creators and players.
Several of the top D&D people who were advocating for players resigned around this time.
WOTC/Hasbro since relented under this pressure, but the bridge was already burned. My group hasn't played a D&D campaign since. We switched to Pathfinder 2e and found that it was a better system altogether.
That was 1999. Invasion came out that year. Innistrad, Mirrodin, Ravnica, and other settings all came out after Hasbro's acquisition.
Every year seems to be the best-selling year so far. Magic: the Gathering is Hasbro's primary revenue source.
And look, I don't like the sheer amount of product they're pumping out every year now. But I realize I'm clearly in the minority opinion based on sales.
In the short term all the franchises have proved incredibly popular (just like in Fortnight), but in the long run I think it means the death of the game (just like where Fortnight is headed).