Well, I reject the argument that "It's D&D, so it must be TB." Tabletop D&D being TB has absolutely zero to do with the gameplay system for a video game. Larian is making a video game here, not a D&D tabletop simulator. That the tabletop version of D&D is TB (which by the way it HAS to be as ALL tabletop games are because that's the only way you can possibly handle a group of people around a table) is in no way an argument that a video game adaptation of D&D must also be TB.

Also, Larian may be "TB specialists" (though there is exactly zero evidence that had anything to do with WotC's choice), but that does not mean everyone loves their combat system, including even everyone who likes TB systems generally. I've seen many people in many forums say they love TB combat but dislike the D:OS system. And for my part, the only reason I will not touch D:OS2, after having tried and hated D:OS1, is the D:OS combat system. It is utterly horrible, even as TB systems go.