This is really, really clearly incestuous tech media stuff as part of a pressure campaign. Sam is the darlin of tech media and he's clearly instigated this reporting because they're reporting his thoughts and not the Board's in an article that purports to know what the Board is thinking, the investors who aren't happy (the point of a non-profit is that they are allowed to make investors unhappy in pursuit of the greater mission!) have an obvious incentive to join him in this pressure campaign, and then all he needs for "journalism" is one senior employee who's willing to leave for Sam to instead say to the Verge that the Board is reconsidering. Boom, massive pressure campaign and perception of the Board flip flopping without them doing any such thing. If they had done any such thing and there was proof of that, the Verge could have quoted the thoughts of anyone on the Board, stated it had reviewed communications and verified they were genuine, etc.
If they do nothing, then public perception harms their ability to raise further capital, and employees leave for Altman's new company. If they cave to the pressure (despite that being objectively the financially right decision), they lose their board seats and Sam comes back, proving they overplayed their hand when they fired him. They're basically in a lose/lose situation, even if this article is sourced from entirely biased and fabricated information. And that's exactly what reveals them as incompetent.
Their mistake was making a move while considering only the technicalities of their voting power, and ignoring the credibility they had to make it. Machiavelli is rolling in his grave...
This is wishful thinking. If an employee is inclined to follow the innovation, it's clear where they'll go.
But otherwise, the point you raise is a good one: this is about the charter of the board. Many of us are presuming a financial incentive, but the structure of the company means they might actually be incentivized to stop the continued development of the technology if they think it poses a risk to humanity. Now, I personally find this to be hogwash, but it is a legitimate argument for why the board might actually be right in acting apparently irrationally.