The Marvel Cinematic Universe is in absolutely no danger of losing its crown as the biggest and most popular franchise in the industry, but the absence of the two characters that defined the Infinity Saga more than most will be keenly felt nonetheless. Tony Stark and Steve Rogers were viewed as the heart and soul of the MCU, and their stories were always intertwined right up until the genius billionaire playboy philanthropist made the ultimate sacrifice at the end of Avengers: Endgame.
Howard Stark was constantly full of praise and admiration for Captain America having been integral to his creation, which led to Tony always being somewhat resentful of Steve, with the former having dealt with some pretty major daddy issues. Still, they managed to strike up a friendship despite there often being an underlying sense of friction between them, and they were even able to patch things up in Endgame following the battle that blew the Avengers apart in Captain America: Civil War.
Of course, the MCU is always known for paying off even the smallest moments years down the line, and a throwaway piece of dialogue in Avengers: Age of Ultron has now taken on a different meaning after foreshadowing Cap’s fate at the end of the Infinity Saga’s final chapter.
After defeating Ultron, Tony made it clear that he was chasing the simple life, something that Steve never imagined he’d get the chance to enjoy. Stark told him, though, that he’d get there one day, and Cap eventually took him up on it by journeying back through time and deciding to stay and live out the rest of his days with longtime love Peggy Carter.
As ScreenRant explains:
As Tony described the kind of life he envisioned for himself, Steve called it the “simple life.” Knowing what was lying ahead for the super soldier, Tony offered some words of encouragement to Captain America, saying, “you’ll get there one day” – referring to retiring from duty and having the same opportunity to live a normal, family life. At that point, Steve was skeptical of the idea, perhaps because it was no longer possible for him to have that with the only person he wanted to share that life with: Peggy Carter. However, as fate would have it, he was given the opportunity to do just that at the end of Endgame.
So, it seems right up until their final moments in the MCU, Steve and Tony’s arcs remained inextricably linked by even the smallest of details in less-regarded movies like Avengers: Age of Ultron.