My understanding is the OpenAI holding company, which is controlled by the board of directors, owns 51% of the capped-profit company, with Microsoft owning the other 49%. There doesn't seem to be a scenario where Microsoft can buy a controlling interest without the boards approval.
MS doesn't have enough leverage to pull such move.
The board could decide to kill the company in MS not only loses a 10 billion invest but has to reconsider its whole artificial intelligence integration push.
MS did have the leverage, and by offering jobs to 700 people at once they felt safe in their move to pressure the board in a way that I'm still quite impressed by. It's probably the most vivid example of the power of the workforce in the 21st century West.
