thinner ionosphere, more gamma radiation, vegans eating vegetation that concentrates gamma?
Roundup.....
I’m more of the opinion it’s just the odds.
With the sheer number of base pairs and number of cells per individual, the chances that the self repair in these cells eventually won’t be able to correct properly and sometimes that will end up as cancer.
Likely enhanced with your noted factors, but hard to tell with only the scant evidence we can dig up from all sources.