Nit: Altman may have orchestrated a coup, but the board certainly did not. The board is the legitimate authority, and in no way is a board firing its subordinate a "coup." Rather, it's executing its legitimate power.
Coups triggered when subordinate feels threatened is a pretty common pattern. IIRC, the recent coup in Niger was triggered when the leader of the presidential guard thought the president was about to fire him, too power in a coup rather than lose his job.