From what's been said a plausible explanation could be the sama was being courted by saudi investors, incl vision fund, to make AI silicon, for 100 billion dollars, and wasn't upfront with the board.
Who knows, total speculation, but definitely grounds for dismissal. Of course he was probably a managed asset, and who knows what kind of complexity is behind the scenes. OpenAI has a very valuable product. Not supporting any ideology here, but the Russian president said that whomever controls AI controls the world. Well, anyway, AI will be a useful tool for technological advancement. It can definitely solve problems.
EDIT: meaning it's important that the AI isn't given problems whose solution harms beings, at all, let alone war- not even by carbon emissions into the atmosphere.