The board wanted to keep the company true to its mission - non profit, ai safety, etc. Nadella/MSFT left OpenAI alone as they worked out a solution, so it looks like even Nadella/MSFT understood that.
The board could explain their position and move on. Let whoever of the 600 that actually want to leave, leave. Especially the employees that want a company that will make them lots of money, should leave and find a company that has that objective too. OpenAI can rebuild their teams - it might take a bit of time but since they are a non profit that is fine. Most CS grads across USA would be happy to join OpenAI and work with Ilya and team.