Marvel: 12 MCU Theories That Make Appalling Sense
7. There Are No Mutants Because Of HYDRA
The Theory
There's a reason - beyond the movie rights issue - why there are no mutants in the MCU (though Deadpool makes a confusingly compelling argument for being on the fringes): it's because HYDRA changed history.
The Evidence
One redditor, called BaronOlio explained that HYDRA stopped Hitler from starting the Holocaust, so young Jewish prisoner Magneto was never imprisoned and never discovered his powers. He thus never met Charles Xavier, the X-Men were never formed and mutants never had a beacon to empower them and encourage them to reveal themselves publicly.
They still exist - the psychic Nick Fury might be one, actually, and the twins' latent powers could be explained as mutations why else would the other test subjects die?) - but they're just hidden and isolated.