I'm sorry did pop culture zeitguiest make you think it was a 1 off on 1 show? this isn't "big bang mentioned D&D in season 4 episode 6" this is a ongoing 5 or 6 year series that a reoccurring main theme is D&D... and it isn't alone. So no not a "Single stand alone advertisement"
by the way when econimies turn down or in general there are emergencies games and toys are the thing that keep selling (well broadly entertainment so movies and sports things too) and when covid hit stranger things was huge and look at that the big boom hit...
oh it also is a HUGE nestolgia for the 80's (I would argue that was a contributing factor not just in D7d but in stranger things that also then fed into D&D)
mean while the concept of "lets plays (both video game and some how TTRPGs) have taken off and we had the luck that one of teh biggest moved from pathfinder to 5e.
it wasn't one stand alone thing... it was the reverse of a perfect storm where everything came togather to make something sell... The fact that 5e was already the compramise edition to bring 4e and PF players both back helped
Now no edition of D&D has been a flop ever, not basic, not 1e, not even my least favorite 3.5... D&D the name sells no matter what and never has there been a true stinker system.
IF the FATAL mechanic was rebranded as D&D the name alone would sell some and all this boom would sell some but the qualify of the worst rpg ever would have still made it fail... but any edition of D&D, or any other game... even ones that have MASSIVE mechanical flaws (shout out to RIfts, I love you worts and all)0 would have soared in this environment.