What if… 615 is the fox universe with mutants and 616 is the MCU and all what happened was a simple change that split the two universes on different paths.
My theory is simply this, sometime during the early 19th century mutants didn’t exist. No wolverine, no magneto, no Professor X, no x-men no mutants. Because of this we get the MCU universe. Super human serum invented leading to Captain America and extra. But if mutants had existed then the avengers and most of the MCU timeline probably didn’t happen. Let me explain.
Super Human Serum & Weapon X Program
In the comics they both happened around the same time and kind of connected but we’re talking movie universe. See in the X-Men world, mutants existed. There for research into creating a super human probably would have been replaced by the weapon x Programmes. Turning humans into mutants. Not everyone knows mutants exist but those that did tried to utilise this in the weapon x programs. So instead of Captain America being the hero of world war 2. It became Wolverine, wolverine literally replaces Captain America. There for Steve Rogers probably never got into the army as no super human program the project probably went to other scientists.
Iron Man & Sentinel Programs.
With mutants starting to appear, sentinels became the suit of armour around the world and based on the x-men films this happened in the 70’s so if sentinels was allowed to continue where does that leave stark industries. Well, there is a lot of implications here. Does shield exist? Maybe Howard stark went to work with bolvair trask. And eventually maybe Tony stark would be working in a trask lab because no obediah stain causing Tony to become iron man.
Avengers & X-Men
With mutants being the bigger threat. Possibly be no Nick fury assembling an avengers. Maybe shield exist but it’s origin is largely connected to Captain America but if no super soldier serum no shield? Well there could be more than one way shield gets invented. So shield could exist but the threat is mutants not humans. So maybe Nick Fury worked or helped Professor X to create the x-men. Ok that’s not in the x-men movies but if Nick who isn’t a mutant needs to create a task force for mutants you could either find someone like Professor x to help him create the x-men but be a silent partner. Or Nick could have been in the background of the weapon x programe. But alas no avengers because you have the x-men
Again, because of Captain America you basically have the response of how shield was created leading to Howard stark and then Tony then iron man and of course hulk. So none of this happens as no super human serum.
Eternals & Apocalypse
It is possible that Apocalypse lays dormant in the MCU. The x-men universe doesn’t really delve too much into ancient history. Other than apocalypse in Ancient Egypt – but say something happened and mutants didn’t exist in the future. No x-men first class characters to awaken apocalypse, then he still lays dormant. Given that apocalypse is embed with celestial technology that too can make sense given we have been introduced to them in Eternals
But if mutants existed wouldn’t Thanos still be looking to wipe out half the universe to stop the Celestials? With infinity stones.
Well maybe not. Remember I said an event that wiped out the mutants sometime in the early 19th century. What if that even was on Titan and Thanos was wiped out and died on his planet when the Celestial awoken. No Thanos no infinity stones right. But how does that lead to no mutants on earth?
Well, with no mutants on earth no need to hide the infinity stones. And one of them could have been used to wipe out mutants. Who would do that? What about a coven of witches? Like Agatha all along?
She’s been around along time. And tesseract is on earth, but so is the reality stone. And what could you change with the reality stone….
And that is my theory.