that's because most of those people did not work for the mission-focused parent OpenAI company (which the board oversaw) but it's highly-profit-driven-subservient-to-Microsoft child company (who were happy to jump to Microsoft if their jobs were threatened; no ding against them as they hadn't signed up to the original mission-driven company in the first place).
it's important to separate the two entities in order to properly understand the scenario here