Well this probably disproves the theory that it was a power grab by Microsoft. It didn’t make too much sense anyway since they already have access to tech behind GPT and Microsoft doesn’t necessarily need the clout behind the OpenAI brand.
Through the public actions of Sam Altman in various places like the US congress it has become rather clear that his goals are to device and fear monger to create an environment of regulatory capture where due to misguided laws OpenAI will have an unfair competitive advantage.
This might be quite in line with what Microsoft tends to like. But it also can be a risk for MS if regulation goes even a step further.
This is also in direct opposition with the goals OpenAI set themself and which some of the other investors might have.
So MS being informed last minute to not give them any chance to change that decision is quite understandable.
At the same time it might have been pushed under the table by people in MS which where worried it poses to much risk, but which maybe e.g. might need an excuse why they didn't stop it.
Lastly is the question why Sam Altman acted the way he did. The simplest case is greed for money and power, in which case it would be worrying for business partners at how bad he was when it comes to public statements not making him look like a manipulative untranslatable **. The more complex case would be some twisted believe that a artificial pseudo monopoly is needed "because only they [OpenAI] can do it in the right way and other would be a risk". In that case he would be an ideologically driven person with a seriously twisted perception of reality, i.e. the kind of people you don't want to do large scale business with because they are too unpredictable and can generally not be trusted. Naturally there are also a lot of other options.
But one thing I'm sure about is that many AI researchers and companies doing AI products did not trust the person Sam Altman at all after his recent actions, so ousting him and installing a different CEO should help increasing trust into OpenAI.