
Just look what Marvel did with Civil War. They introduced a relatively unknown character (Black Panther), and they reintroduced a familiar character that had been damaged by bad films (Spider-man). Both characters and both films benefited in a huge way from Civil War.
With 10 minutes of Reed Richards/Victor Von Doom screen-time in an upcoming film, they could completely reinvigorate interest in the Fantastic Four.
Fox may not like the fact that Marvel can make money with FF while they can't, but continuing to throw money away on the FF won't change that.