Which is to say, they were likely Altman supporters. Which is fine! They’re free to do as they wish.
However if that’s it (and it does remain to be seen if more happens or not) than 2/3 of folks stand by the decision, which would match with the board votes
I haven't seen that reason yet, though I don't rule out one exists and even then you'd have to do this in a way that it doesn't ruffle the feathers of your ultimate paymasters. Being a board members of a large company is an exercise in diplomacy, not in bull-in-a-china-store level incompetence.