Leave 'em wanting.
Leave the players wanting, seeing a concept so fun and well executed as to AB test a new franchise.
Leave the developers wanting, having briefly tasted the dream of working on a budgeted project to make beautiful art.
Hold promises of it happening again, it actually happening all the way to completion, over the heads of them both. Each new month waiting another subscription fee, another quarterly report. They have other content units to chew on, developers and players alike.
Your game cannot be perfect, for then you'd be irreplaceable. Growth means room, and the people making things which already work are in the way. The future must be attainable as a contrast to a broken present, so we're presented with a broken present.
Games are a gift, and Microsoft wants next quarter's gifts to be worth paying for.
It doesn't matter the accolades, the money made. It doesn't matter how many subscriptions, reviews, conscriptions or views. Profit provable is not profit replicable, as labor conditions and game expectations improve so too do costs.
Churn is the default state of the industry, for if developers were allowed to rest, they'd unionize. And then creating content units at scale per stakeholder expectation would be impossible.
Humans cost money, and the longer they work, the more bargaining power for fair labor compensation they have. Take the workers out of the environment they've cultivated which could almost be mistaken for a comfortable art studio. Stop them flourishing unprofitably, and failing that, stop them altogether.
A single developer with a vision who refuses to work under Microsoft is a threat and must be culled. An entire development team would risk competing with current operations.
Microsoft is building an empire using the labor and eventual corpses of developers they see as threats to their very existence. It's best to keep developers themselves underdeveloped, output compromised by conditions anathema to learning. Swap out the warm bodies on projects as needed to keep them making platforms instead of playspaces.
If developers get a chance to be too successful, they'll potentially take that success somewhere we can't profit from it. But since they're asking for money and respect as human beings, get rid of them and get some fresh meat.
This is Microsoft culling the herd. Phil Spencer can act benevolent all he wants as he keeps the flock tender and kind before his company pulls the trigger.