I agree with you on the percentages, funny enough, and that’s why it doesn’t explain the game’s success to me. If D&D was responsible, there’d be far more people picking up the enhanced editions of the first two games, Neverwinter Nights, etc., and the MMO would be way more popular. If it was 5e, Solasta would have set the world on fire years earlier. I just don’t see it as the largest contributing factor when I’ve seen plenty of examples of people surprised to learn that the game is tied to Dungeons and Dragons after they’ve already started playing it.
D:OS2 sold several million copies btw. Maybe that doesn’t quite count as mainstream, but it was already a healthy increase from what the first game sold, so they were trending up already.