Whether fulfilling their mission or succumbing to palace intrigue, it was a gamble they took. If they didn't realize it was a gamble, then they didn't think hard enough first. If they did realize the risks, but thought they must, then they didn't explore their options sufficiently. They thought their hand was unbeatable. They never even opened the playbook.
That would imply they couldn’t have considered that Altman was beloved by vital and devoted employees? That big investors would be livid and take action? That the world would be shocked by a successful CEO being unceremoniously sacked during unprecedented success, with (unsubstantiated) allegations of wrongdoing, and leap on the story. Generally those are the kinds of things that would have come up on a "Fire Sam Pro and Cons" list. Or any kind "what's the best way to get what we want and avoid disaster" planning session. They made the way it was done the story, and if they had a good reason, it's been obscured and undermined by attempting to reinstate him.