I don't think this is a fair conclusion. Close to 90% of the employees have signed a letter asking for the board to resign. Seems like that puts the burden of proof on the board.
A board that basically accused Altman, publicly, of wrongdoing of some kind which appears to be false. To bring Altman back, or issue an explanation, would require retracting that; which brings in serious questions about legal liability for the directors.
Think about it. If you are the director of the company, fire the CEO, admit you were wrong even though nothing materially changed 3 days later, and severely damaged the company and your investors - are you getting away without a lawsuit? Whether it be from investors, or from Altman seeking to formally clear his name, or both? That's a level of incompetence that potentially runs the risk of piercing into personal liability (aka "you're losing your house").
So, you can't admit that you were wrong (at least, that's getting risky). You also can't elaborate on what he did wrong, because then you're in deep trouble if he actually didn't do anything wrong [1]. Your hands are tied for saying anything regarding what just happened, and it's your own fault. All you can do is let the company implode.
[1] A board that was smarter would've just said that "Altman was a fantastic CEO, but we believe the company needs to go a different direction." The vague accusations of wrongdoing were/are a catastrophic move; both from a legal perspective in tightening what they can say, and also for uniting the company around Altman.
