Um…Sony was in talks to pay for Starfield to be a PS exclusive - which would have taken it from PC for a year and from xbox permenantly - until MS bought Beth.
Also, Starfield is a new IP, not an “already existing and widely popular” one…
I’ll also mention that Phil Spencer publically admonished and fought against exclusivity agreements for years. He has said in interviews both private and public that he prefers a world where there are no exclusives. Until the market spoke and declared “exclusives” to be the measuring stick of a platform’s health, thus forcing his hand. And now here we are.