I think it's a stretch to assume he was "beloved by his employees," because they signed that document. Some of those very same people have resigned (https://www.fastcompany.com/91126785/openai-resignations-are...), which is not someone you typically do if you love your boss that much.

Other possibilities are far more plausible. Like fear of reprisal if Altman returned coupled with fear he could cause OpenAI to implode if he didn't, wanting to hit the startup jackpot instead of working for a nonprofit, etc.

However someone was going around asking them to sign a specific document, which opens up many other possibilities.

I’d seriously consider quitting on the spot if my boss at any place I’ve worked in the past asked me to sign something like that. Not signing isn’t quite the same thing as quitting, but there’s a clear implication not doing so would seriously damage any long term prospects at the company.