Are you familiar with the superhero industry at all? Because adaptations of superhero properties have always been popular to attempt and probably always will be. The 2000-2014 era is definitely an aberration, but superheroes stopped being a fad when Captain America socked Hitler in the jaw.
I think it’s partly a fad and that part will fade. But I think a more long-term change is the improvement of film technology. It’s now possible to make a superhero movie that looks believable on screen. Back in the seventies and eighties, a top-notch movie like Superman or Batman might get the audience to overlook the cheesy-looking effects but nowadays you can sell a superhero movie on its effects.