I experienced and saw bullying to a large degree at many levels. It is possible that being a military brat put me in an environment where there might have been more of it (people coming and going, constantly having to prove themselves or measure up in new environments, etc) but I don’t think so.
I think it is a part of the human condition, and it starts at a young age.
Just my opinion.
I don’t put all that much store in Darwin but natural selection in the form of survival of the fittest is observable in most species and humans are far from immune. Be different, expect the crowd to try to force conformity or force you out, it happens again and again although people are very prone to assigning other motives. It can get ugly.