Marvel is a film company first and furthermost and everything they do is to boost that. Why should they promote X-Men when someone else makes the vast majority of the money on it? It undermines what they do as a company.
Nintendo putting Mario on Sony's platform boost Sony's money. Sure Nintendo makes money off the game they make but doing so undermines what they do as a company in the same way Marvel putting any sort of heavy promotion on the X-Men undermines their business plan.If anything they should use the X-Men to boost the characters they actually have the movie rights to.
You and people like you are a part of a small vocal minority that are displeased with the way they run the company. It's not like fans have mobilized and boycotted the films or the comics over this. Most people don't care.
Who is benefitting from this?
Name 1 person who comes out the winner in doing this.
Fox's films are bigger than ever.
Marvel isn't getting the rights back.
Marvel is losing revenue from one of their biggest comic properties.
The fans are losing because they don't get books from their franchise
The video games will suffer because they aren't allowed to use certain characters. A lot of people are complaining already about marvel vs capcom
There is literally not 1 benefit to marvel on the business side.
And again ,your mario on Sony Comparison doesn't make any sense.