They would probably have to ask for permission to use his name. Other people who have their own celebrity bot on chess.com, are affiliated to chess.com, Magnus is not.
But Mangus is #1 on Chess.com in Blitz and Bullet
does that mean that these celebrities promote chess.com??

Magnus represents chess24.com which is a rival website, so he is not affiliated with chess.com and thus he doesn't have a bot
Chess24 was bought out by chess.com.