In Fallout 1 and 2 the nature of ghouls was a bit more vague and it was implied that they were all exposed to small concentrations of aerosolized FEV, likewise with deathclaws and radscorpions and such
Bethesda kinda put that by the wayside which tbh is fine, it's supposed to be 1950s super science after all
Just hear me out, ok? What if we had a god machine and in process of reformatting reality to put ourselves onto the throne of everything which don't require more than one day of travel by boat cause we're apparently allergic to water some oopsies happened? Would that be ok or not ok? Nobody would know anyway?