I think this was a unique situation due to timing. OpenAI had 9 board members at the beginning of the year, but 3 (Reid Hoffman, Shivon Zilis, and Will Hurd) had to leave for various reasons (e.g. conflict of interest, which IMO should have also taken D'Angelo off the board), and this would have never happened if they were still on the board. So you were left with a rare situation where the board was incredibly immature/inexperienced for the importance of OpenAI.

It has been reported that Altman was working on increasing the size of the board again, so it's reasonable to think that some of the board members saw this as their "now or never" moment, for whatever reason.