Time travel is a tricky little thing there are various complications attached to it and nobody really knows how this thing works. The multiple perspectives associated with Time travel are a bit fastidious.
So things are pretty hard to get it right especially When your entire billion-dollar blockbuster flick rest on it, the stakes are even higher. This has to lead a confusion between the writers(Stephen McFeely and Christopher Markus) and directors(Russo Brothers)of the movie and to disagree over each other.
** This goes without saying the following article contains spoilers for Endgame **
During the final scenes of the movie, we see Captain America(Steve Rogers) going back in time to return the Infinity Stones to where they found them but he stays back there and lives out his life with the love of his life Peggy Carter.
And now the question arises, has Cap been living in the past this entire time or did he go and live in another dimension?
The Russo Brother’s Take
“As Steve went back into the past and lived there, Steve’s choice leads to a branched reality”.
And now the Endgame writers Christopher Markus and Stephen McFeely in an interview with Fandango, revealed that they do not think Steve had created a new reality at all.
The Writer’s Take
Christopher Markus: That is our theory. We are not experts on time travel, but the Ancient One specifically states that when you take an Infinity Stone out of a timeline, it creates a new timeline. So Steve going back and just being there would not create a new timeline. So I reject the “Steve is in an alternate reality” theory.
I do believe that there is simply a period in world history from about ’48 to now where there are two Steve Rogers. And anyway, for a large chunk of that one of them is frozen in ice. So it’s not like they’d be running into each other.
Both the explanations lack a certain clarity both the parties fail to answer the question on how did he(Captain America) suddenly jump backcrossed timelines at the end?
Each way, it is rather disheartening to see the four most significant people associated with Avengers: Endgame does not seem to click with each other on a hugely mattering plotline.