Using that framework, I still think it is possible that this is the result of legitimate and irreconcilable differences in opinion about the organization’s mission and vision and execution.

Edit: it is also common for changing circumstance to bring pre-existing but tolerable differences to the relevant Forefront

Yes, and if that is so I'm sure there are meeting minutes that document this carefully, and that the fall-out from firing the CEO on the spot was duly considered and deemed acceptable. But without that kind of cover they have a real problem.

These things are all about balance: can we do it? do we have to do it? is there another solution? and if we have to do it do we have to do it now or is there a more orderly way in which it can be done? And so on. And that's the sort of deliberation that shows that you took your job as board member serious. Absent that you are open to liability.

And with Ilya defecting the chances of that liability materializing increases.

I see your point.