The board has no responsibility to Microsoft whatsoever regarding this. Sam Altman structured it this way himself. Not to say that the board didn't screw up.
Between Bing, o365, etc. etc. etc. it's possibly they could recoup all of the value of their investment and more. At the very least it is a significant minimization of the downside.
I'd imagine the latter, and that it can be easily yanked away.
Besides, even if you had an outstanding contract for $10bn, a judge would not pull a "well technically, you did say <X> even though that's absurd, so they get all the money and you get nothing."
And a bunch more. A lot of you will never have heard of them, but all of them are multi billion dollar behemoths with thousands of subsidiaries, employees, significant research and investment arms. And they love the fact that barely anyone knows them outside Germany.
Nothing stopping a non-profit from owning all the shares in a for-profit.
[1] https://finance.yahoo.com/news/top-10-holdings-mormon-church...