Levistus's_Leviathan
5e Freelancer
Alternatively, they could use the Snap/Blip as an explanation for mutants. They could say something like, "For reasons unknown to us, a small percentage of the population that was Blipped had their genome partially rewritten after they came back, mutating them and granting them strange and unique abilities."Only a small number of people have encountered the Hex. I don't think that is going to explain mutants, worldwide.
Or, they could just use the Multiverse. Either could work, but would have different and interesting consequences.