What do you think the leader of multiple billion dollar companies would be doing exactly? People like Musk are like conductors of an orchestra. That's not easy, especially with multiple successful companies.
SpaceX and Tesla have the equivalent of the principals of each section of the orchestra feeding their conductor his cues and making sure he gets them right. Google has someone standing on the podium and bowing, but nobody waving the baton at all.
OpenAI is more of a research organization than a product company, and so it's hard to see where someone like Altman can contribute meaningfully to the direction.