Huge blow to Google.

I doubt that the money had anything to do with it.

I also doubt that the state of the technology at OAI vs. Google had much to do with it, Google is behind no doubt, but the gap is not as far as we know, insurmountable.

I suspect that this is a leadership clash. Noam was working in GDM. GDM somehow went away from coding and RSI into "world models" and that has played out very poorly. Who made that call? Who was still playing politics?

Given this is Noam the list of people that could be pissing him off is very small: Demis, Sergey (?!), a couple of VPs in GDM.

What the hell happened?

It's entirely possible he got in a flame war over political issues with other Googlers and Google asked him to leave.