My sense is that many companies spun up various roles in part to be seen as doing something about various things. With the pullback in tech, even if the people in those roles weren't actively pushed out, the smarter ones probably saw which way the wind was blowing.
If you’re OpenAI you have to have an ethics department even if you don’t care at all, because otherwise it looks bad (“they don’t even have a head of ethics!”).
So it’s entirely possible you end up in a situation where you have a highly paid, fairly prominent head of ethics whose actual job is mostly just saying they’re the head of ethics, with little actual power or influence.
Ambitious people won’t tolerate that for long and they’ll move on