Summary

• Bruce Banner's intense experiences and constant losses motivated him to become Smart Hulk in Avengers: Endgame.
• The events of Age of Ultron, Ragnarok, and Infinity War unfolded over a single week for Banner's human persona, impacting his character.
• Banner's guilt over losing to Thanos in Infinity War and his history of losing back-to-back battles explain his controversial transformation in Endgame.

Mark Ruffalo's Bruce Banner, a.k.a. the Bruce Banner's MCU timeline reveals why these happened.

While MCU adaptation of World War Hulk. Banner has had an intense history in the MCU, but his jam-packed timeline has informed his more recent, divisive decisions.

Bruce Banner Experienced Age Of Ultron, Ragnarok & Infinity War In Only 1 Week

Even though there were three years between 2015's Avengers: Age of Ultron and 2018's Avengers: Infinity War, Mark Ruffalo's Bruce Banner actually experienced the events of these projects and 2017's Thor: Ragnarok in less than a week. Banner was last seen in his human persona prior to the Battle of Sokovia in Age of Ultron, before Natasha Romanoff awakened the Hulk to aid in the fight against Ultron's army. Following the battle, the Hulk exiled himself and inadvertently made his way to Sakaar, where he remained trapped as the Hulk for two years, which saw him become the Grandmaster's champion.

During Thor: Ragnarok, the Hulk reverted to Bruce Banner, but since the personas were separate - with neither ing the exploits of the other - Banner experienced the events of Age of Ultron only moments previously. Shortly after the Hulk helped Thor and the Revengers battle Hela on Asgard, the Mad Titan Thanos attacked their refugee ship, leading directly into the events of Avengers: Infinity War. Several days may have ed for Bruce Banner, but the events of these three epic projects unfolded over a single week for Banner's human persona, which surely had a major impact on the hero.

Banner Felt More Guilt Than Others About Losing In Infinity War

During 2019's Avengers: Endgame, which took place five years after Infinity War, Banner explained how he felt more guilt over losing to Thanos than any other Avenger. He noted that it was like he lost twice, with the Hulk failing to defeat Thanos aboard the Asgardian refugee vessel, and then again when Thanos collected the Infinity Stones and snapped his fingers. This underlined the tragedy of Banner's experiences during Infinity War, during which Banner struggled with the Hulk's refusal to the battle, but is made worse by the fact that Avengers: Age of Ultron had happened only moments earlier.

While Bruce Banner and the Hulk may have lost twice in Infinity War, his recent experiences of not knowing how the Battle of Sokovia ended, finding himself trapped on Sakaar, and being unable to take down the mountain-sized Surtur on Asgard mean he actually lost several times before fighting Thanos. This must have had an enormous strain on his ability to function in his right mind as a genius-level scientist or as a powerful Avenger. However, the impact of these experiences may explain exactly why Banner's most controversial transformation occurred in Endgame​​​​​​​, as Banner's "Big Week" must have changed him.

Banner’s Big Week Answers Why He Wanted To Become Smart Hulk

The fact that Bruce Banner missed so much time being trapped as the Hulk, with him experiencing Age of Ultron, Ragnarok and Infinity War in only a week, explains why he became Smart Hulk in Avengers: Endgame. Banner's constant losses would have motivated him to combine his human and Hulk personalities, allowing him to utilize the full power of his brains and brawn in future battles. Hot on the heels of intense internal conflicts with the Hulk, as well as back-to-back battles with villains such as Ultron, Hela and Thanos, Bruce Banner's transformation into Smart Hulk actually makes complete sense.