Clearly Microsoft staked its whole product roadmap on 4 random people with no financial skin in the game.
You actually think that for-profit corporate boards are significantly different, especially in the startup/early IPO phase?
The board reports to the shareholders and the management reports to the board.
In early stage companies it is possible and likely that all three are the same person, that doesn't change the different fiduciary responsibilities for each role they play.
This has not do with beneficial ownership of the underlying asset alone. Principals sometimes do not have that relationship. Asset ownership is a common way to benefit from a entity, but not the only way.
Specifically here Sam Altman does not own shares in the for-profit entity and non profit entities do not have shares.
I don't have direct knowledge on how OpenAI handles it, however it is not uncommon to do revenue sharing, or lease an underlying asset like a brand name (WeWork did this) from the Principal directly, or pay for perks like housing, planes etc, or pay lot of money in Salary/Cash compensation, there are myriad ways to benefit from control without share ownership.