Marvel loves cucking. Look at Slott. First chance he got he got he made Marconi kiss her new black love interest in front of Doc Ock (Fell in love with her during Superior Spiderman). Then we got the Bendis the cultural Bandito making every character he can cheat or revert back to to simpler character. Like Cyclops with Emma with Namor.
You also have Deadpool marrying a literal immortal whore who outright tells him shes going to bang any guy she wants.
Its forced drama, especially to casual readers who just want to see people with powers beat the shit out of people with other powers.
As for BB and Medusa it just come comes down to writers not giving a shit anymore. There is only so much you can do with Medusa. Most normies don't care about her. At least Black Bolt is relatively interesting even if he is okay with his wife fucking other men. It did dampen my liking on the character. Alth