Question: Why was Edward Norton replaced by Mark Ruffalo as Bruce Banner?
TedStixon
18th May 2023
The Avengers (2012)
Answer: There were disagreements between him and Marvel about the contract. It's said Norton didn't want to be clung to a single character.
Answer: In addition to lionhead's answer, there are also rumors that Norton wanted more creative control over the character and franchise, as evidenced by the fact he did frequent uncredited rewrites on the set of "The Incredible Hulk" and also even ghost-directed a few scenes while director Louis Letterier was tied up with other obligations. Given the complexity of the MCU, the producers and studio didn't necessarily want cast-members to exercise more creative control over the films early on because it could undermine their long-term plans.
TedStixon