It's outselling is what caused Microsoft to not deny it. It originally denied it because they had a rule that games needed feature parity with both Series X and S. BG3 split screen couldn't be done on S. The massive success is what led them to relax the rule. And virtually no one saw this level of success coming from within the gaming industry, including the developers themselves.
Edit: I just realized this is being upset about Starfield.
That is totally the fault of gamers. The biggest reason given for buying a PS5 over Xbox was exclusives. What the fuck did you think was going to happen? Sony started the exclusives battle and continually came out ahead. Obviously MS is going to fight. Making exclusives such an important decision in console purchases drove exclusives to be important overall. There's no sense in being upset that the industrynis literally responded to gamer's actions and stated motivations.