* Edward Norton's Departure: Edward Norton portrayed the Hulk in *The Incredible Hulk* (2008), but creative differences with Marvel Studios led to his departure. They were looking for an actor who would be more collaborative and comfortable with the Marvel Cinematic Universe's (MCU) overall vision.
* Ruffalo's Acting Abilities: Mark Ruffalo is a highly respected actor known for his versatility and ability to portray complex characters. Marvel recognized his ability to convey both the rage and vulnerability of the Hulk.
* Physical Transformation: While Ruffalo isn't built like a typical action hero, his performance emphasizes the Hulk's internal struggle and emotional depth. Special effects and motion capture technology were used to transform Ruffalo's appearance into the Hulk.
* Chemistry with the Cast: Ruffalo's chemistry with the rest of the Avengers cast, particularly Robert Downey Jr. as Iron Man, was excellent. They brought a unique dynamic to the Hulk's character and helped create memorable scenes.
Ultimately, Marvel chose Mark Ruffalo because he embodied the complex character of the Hulk in a way that resonated with audiences, blending the character's physicality with his emotional turmoil.