I am pretty positive on AI and LLMs and all this stuff. But even so I really doubt OAI could have made something so much better than GPT to the point that it worth sacking its CEO in such a manner.

Sam has always been a salesman, that is true and the board knows it. It would take much more than just a disagreement on the value and urgency of a deal to get rid of him. I think it has to be active sabotage and some kind of business maneuver that basically kill the company as it is right now while not telling the board about it.