Veganism can act as cover for disordered eating; perhaps that is what you have observed.
Related, I know many “vegetarians” who are what I call effective vegans, meaning they eat vegan ~90% of the time, recognizing purity as a pointless pursuit.
Just saying, my experience with vegans is very limited. For all you know, the vegans you know are, in fact, cancer patients. Cancer patients are much less rare than vegans after all. Not everyone tells the people around them.
That sounds like the vegetarians I know. The vegans I know look like cancer patients.