"massively successful" in the context of Larian's entries in the Divinity series or even Pillars of Eternity, which moved almost three quarters of a million units in its first year on sale, don't count as successes in the eyes of AAA publishers like EA or Ubisoft. Dragon Age: Inquisition moved more than a million copies in its first week on sale, was Bioware's biggest launch (probably ever, given the current state of the studio), and still barely made an impression in EA's bottom line. In the same year FIFA 12 sold 3 million copies in its first week, and with its Ultimate Team gacha system represented a much longer stream of ongoing revenue than anything a self-contained single player RPG could provide.

Not to mention, deep single-player RPGs are massive undertakings, that appeal to a somewhat fickle playerbase. EA and Activision have demonstrated with FIFA, Madden, and CoD that they can cheaply reskin the same game over and over on an annual basis and move multiple millions of copies each time, without making an effort. Why take a risk on a relatively niche genre where your game could flop because of an off story beat or wonky mechanic, when you can just stick your last megahit in the photocopier and have it poop out another nine-figure megahit?

BG3 is of course a massive success and should be celebrated, but big publishers want to maximize their return on investment, and right now that means wedging live service offerings, loot box mechanics, and micro transactions into whatever genre maintains the most engagement over time. Right now that means multiplayer shooters and sports games.