Board games and war games are a much, much, much larger market than pen & paper. Traditional games as a market is surprisingly big and growing, but the money is in expandable games, collectibles, and miniature based games. Games like D&D are in a super small market, but D&D itself was still well over half the market at its smallest (unless you really want to say Pathfinder isn’t functionally D&D). It’s dominated for decades for no tangible reason.
If you look at other long running series like Traveler or RuneQuest, Frank Chadwick or Steve Perrin are distinctly less interesting names. I wonder if “Gygax” fed into the Satanic Panic surrounding the game.