If you don't think there would be a shareholder revolt against the board, for simply exercising their most fundamental right to fire the CEO, I think you're missing part the picture.
If they were super-duper worried about how Sam was going to cause a global extinction event with AI, or even just that he was driving the company in too commercial of a direction, they should have said that to everyone!
The idea that they could fire the CEO with a super vague, one-paragraph statement, and then expect 800 employees who respect that CEO to just... be totally fine with that is absolutely fucking insane, regardless of the board's fiduciary responsibilities. They're board members, not gods.
I still believe in the theory that Altman was going hard after profits. Both McCauley and Toner are focused on the altruistic aspects of AGI and safety. Altman shouldn't be at OpenAI and neither should D’Angelo.
But why would anyone expect 800 people to risk their livelihoods and work without a little serious justification? This was an inevitable reaction.