In 2008, Marvel was on the ropes, or at least the movie-making part of the business was. Just look at the last eight movies featuring Marvel characters released before April 2008:Blade Trinity, Elektra, Man-Thing, Fantastic Four, X-Men: The Last Stand, Ghost Rider, Spider-Man 3 and Fantastic Four: Rise of the Silver Surfer. Average Rotten Tomatoes score of those eight movies: 33 percent (which, by the way, is terrible).
Seeking improvement, Marvel Studios took full control of several characters and planned an ambitious “universe” of movies, where different heroes in different films would interact with each other and get together once every few years to make The Avengers. Of course, for it to work, the entire investment was based on making movies that people, you know, liked.