As much as I dislike Microsoft: they played this exactly right. No boardseat: no culpability or conflict of interest, catch the falling pieces and reposition themselves stronger. What makes you say they didn't anticipate the problem? If they had anticipated it I don't see what else they could have done without making themselves part of the problem.
1. When they invested in Open AI it had a more mature board (in particular Reid Hoffman) and afterwards they lost a few members without replacing them. That was probably something Microsoft could have influenced without making themselves part of the problem.
2. They received a call one minute before the decision was made public. That shouldn't happen to a partner that owns 49% of the company you just fired a CEO from.
Yes, but both of those are not Microsoft's doing but the OpenAI board's doing. You don't just get to name someone to a board without the board to agree to it and normally this happens as a condition of for instance an investment or partnership.
Nadella was rightly furious about this, the tail wagged the dog there. And this isn't over yet: you can expect a lot of change on the OpenAI side.
Yes, that probably was a mistake, it should have come with more protections. But I haven't seen any documents on the governance other than what is in the media now and there is a fair chance that MS did have various protections but that the board simply ignored those.