previously there wasn't an extremely profitable, market leading, privately owned gaming company with a founder that is completely and utterly determined to ditch Microsoft
and share the result of that freely with the world
I am an employee of a well known Fortune 500 consulting company, but definitly not Microsoft, better luck with your search next time.
Microsoft is a company, there is no such thing as honour for business, only money and profits.
Same applies to dumb quotes like "do no evil" and similar.
You're right, Windows isn't the main target platform for AAA game studios, Playstation, XBox, Switch, iOS and Android are the ones briging big bags of money home.
Those 2% market shared are filled with games that are developed on Windows, targeting Windows.
Meaning those game studios will keep giving Microsoft money, and letting Valve do the needful to work on their platform.