So her move wasn't stupid at all. She obviously knew people working there respected the leadership of the company.
If 550 people leave OpenAI you might as well just shut it down and sell the IP to Microsoft.
Do you not trust Microsoft's public statement that jobs are waiting for anyone that decides to leave OpenAI? Considering their two decade adventure with Xbox and their $72bln in profits last year, on top of a $144bln in cash reserves, I wouldn't be surprised if Microsoft is able (and willing) to match most comp packages considering what's at stake. Maybe not everyone, but most.
Actually for MS this might be much better cause they would get direct control over them without the hassle of talking to some "board" that is not aligned with their interests.