But the Iron Man and the Mad Titan aren't so different, as they are both futurists hoping to prevent horrible things from happening. Thanos is just willing to commit genocide on a universal level to achieve his goal.
A new fan theory attempts to square away why they do what they do, addressing Thanos' line of being "not the only one cursed with knowledge," as well as Stark's own visions and dreams of future events. Take a look:
All in all, the theory is pretty sound, but it doesn't take into account that many of these movies are made by separate film makers. While they are all likely collaborating on a macro scale, incorporating all of these events is likely more of an "a-ha" moment the filmmakers had in cracking the story than some intricate plan laid in the early stages of Avengers: Age of Ultron.
That said, while these kinds of stories are generally frowned upon in some stories, as not everyone in the audience is familiar with every single thing that's happened before, the Marvel Cinematic Universe is different. Avengers: Endgame is the culmination of everything that's happened prior to this film.
A lot of expectations are riding high on Avengers: Endgame, and directors Joe and Anthony Russo are fully aware of the challenge they're facing. But they're aided (or harmed) by the fact that this movie was mostly set before Avengers: Infinity War even hit theaters, so they weren't able to change a lot based on the fan reaction.
Instead, they set out to make a movie that interested them as storytellers, according to their comments to Business Insider.
"When Joe and I got hired to direct [Captain America:] Winter Soldier, that movie was many multiples larger than anything we'd ever done before as filmmakers," Anthony said. "But the way we work as filmmakers is we have to satisfy ourselves first and foremost. If we're making a movie that excites us, that's the best we can do. We can't predict if people are going to like it, we just know whether we like it. That's how we've made every one of our Marvel movies and it's how we're making this one. For all of the anticipation and anxiety about it, nothing serves Joe and I better than staying focused on the story we're trying to tell and telling it the best way we can."
Avengers: Endgame premieres in theaters on April 26th.