Greg's removal was announced in the same press release as Altman's

ah ok. I thought the board decided to remove Altman, then Brockman quit in response, so there was no deliberation about his (Brockman's) removal.

He was renoved as Chairman at the same time (close enough that they were announced together, and presumably linked in cause, though possibly a separate vote) as Altman was removed as CEO.

ah ok makes sense. I thought he just resigned in response to Altman's ouster, so there was no board decision to remove Brockman.