I can't speak to Helldivers, but pinning Baldur's Gate 3's success on the recent growing popularity of the D&D franchise is beyond reductive. There's no huge publisher for Baldur's Gate 3; Larian's a licensee and an independent studio to boot, and Hasbro's not running massive marketing campaigns for them any more than Disney is for the typical licensed Star Wars game. There's also the game's pay-once sales model, which is something else you get when you're not beholden to publishers or public shareholders.

BG3 was the culmination of decades of iteration by Larian and was the studio's first attempt with a AAA budget. The game has more in common with Divinity: Original Sin 2 than it does Baldur's Gate 2, as the Baldur's Gate die-hards would be happy to tell you.

Calling CRPGs a popular genre is also going to get some laughs. Sure, we might be able to look on this point now in a few years as when CRPGs went mainstream (or maybe not, as the insane amount of choice built into the game set the bar so high that it's possible no one's going to bother with that kind of risky content-making). But by the time Larian started development on BG3, the genre had just risen from the dead after some successful Kickstarter campaigns and was still very niche.