Exactly this - if not at all about hours spent (at least that’s not a good metric; working less will benefit a burned out person; but the hours were not the root cause). The problem is lack of autonomy, lack of control over things you care about deeply. If those go out the window, the fire burns out quickly. Imho when this happens it’s usually because a company becomes too big, and the people in control lack subject matter expertise, have lost contact with the people that drive the company, and instead are guided by KPIs and the rules they enforced grasping for that feeling of being in control.