I think that's a nothing-burger but it's enough to force him out. They probably have more cards in the play. Unfortunately we will never know of them.
Quid pro quo sexual harassment is not a “nothing-burger”.
You don't think the board of a listed company care about the CEOs bit on the side is being promoted? That's really not a good look for a company to admit that.
Having sex with a report is a very serious no no. There are very valid questions of one's ability to consent when your boss is also your partner.