This is probably what prevented the Stadia team from doing the same thing. Lot‘s of people saying: „why not partner with valve/steam for their library“. Because it‘s not Valves library to begin with. This was inevitable. No publisher cared about GFN playing their games in the cloud in the beginning. Just like studios sold off their content to Netflix for pennies in the beginning. It was free money and they didn‘t have a use for them anyways.
Now they smell money and opportunity to fleece a bigger company for higher fees. It happens all the time, unfortunately.
That‘s why it‘s pretty disappointing that stadia killed their first party studios. You have to produce your own content (like netflix) or at least partner with publishers to be exclusive or simple. This seems to be happening with Ubisoft.
But MS just has such a massive advantage with Gamepass.