- peer pressure
- group think
- financial motives
- fear of the unknown (Sam being a known quantity)
- etc.
So many signatures may well mean there's consensus, but it's not a given. It may well be that we see a mass exodus of talent from OpenAI _anyway_, due to recent events, just on a different time scale.
If I had to pick one reason though, it's consensus. This whole saga could've been the script to an episode of Silicon Valley[1], and having been on the inside of companies like that I too would sign a document asking for a return to known quantities and – hopefully – stability.