Thanos’ actions in the MCU were a source of great trauma. And given that Earth was ground zero for at least 3 iterations of the snap, it could be the reason that mutants are finally coming to the MCU.

The MCU has hinted at mutants in its main universe via certain easter eggs in its streaming series. She-Hulk teased ‘a man who fights with metal claws in bar brawl’, while Ms.Marvel was heavily implied to be a mutant at the end of her own show, with Bruno Carelli talking about there being a ‘mutation’ in Kamala’s DNA, accompanied with the soundtrack of X-Men: The Animated Series.

It must be noted that all these Easter Eggs popped only in Phase 4, after the Avengers defeated Thanos and his army, implementing the full power of the Infinity Stones no less than 3 times on Earth: Once when Thanos snapped away half the life from the universe, once when they were brought back by Smart Hulk and another time when Tony Stark used the stones to defeat Thanos’ army.

Given that it is known that the Stones emit a readable amount of radiation and that using them sends out a universe-wide surge of energy, a Reddit theory has come out suggesting that The Infinity Stones might be directly responsible for activating the dormant X-Gene in Earth’s population.

The Infinity Stones could have ushered in the Age of Mutants in the MCU

A theory on Reddit, put forward by u/Caturtle_21, posits that The Infinity Gems could have caused the X-Gene in multiple people to be activated via the traumatic events that they had to face come The Blip. However, there is more to the theory, given that it is explored in the comments section of the post, which highlights a slew of other ways The Blip and the return of humanity five years later could have triggered the emergence of the Mutants.

u/NeedleworkerAgitated pointed out that the stones release a massive amount of energy and have a gamma signature, which could have resulted in them making the mutants in the mainline MCU timeline. This is corroborated by the fact that Scarlet Witch and Quicksilver got their powers after they were experimented on with the Infinity Stones, which would also explain why Mutants are only popping up since Phase 4, rather than before. This would also explain how Monica Rambeau got her powers via Wanda’s hex.

The Sacred Timeline’s lack of mutants could be explained by Kang’s worries

It is interesting to note that while The Fantastic Four and the X-Men seem to co-exist with the Avengers in most universes, or even exist without them, the Universe without either the Fantastic Four or the X-Men is considered the Sacred Timeline. It is possible that Kang had no trouble in defeating the Avengers, but given that the X-Men and the Fantastic Four have some of the smartest people in the Marvel Universe, Kang might have nipped their existence in the bud, causing them to be labeled as aberrations.

The Fantastic Four and the X-Men could be the key for the Avengers to defeat the Council of Kangs. Now that an Avenger, by himself, was able to defeat a version of Kang on his own, the council might see it as thier best ineterst to wipe out any sort of super powered entity, which would make the Sacred Timeline a world where no superheroes exist, which could lead to Secret Wars, as superheores from various universes fight a host of Kangs at the End of Time, making it into Battleworld.

While characters like Namor, a mutant who has existed in the universe for a while, the fact that they were revealed in Phase 4 could point towards the fact that Kang’s hold on the timeline has slipped, especially in the wake of Loki’s war against He Who Remains.