This event was more than just a costly signal. The costly signal would have been "stop doing what you're doing or we'll remove you as ceo" and then not doing that.
But they did move forward with their threat and removed Sam as CEO with great reputational harm to the company. And now the board has been changed, with one less ally to Sam (Brockman no longer chairing the board). The move may not have ended up with the expected results, but this was much more than just a costly signal.