I've picked on a few kids back in middle school, and the reason for it was super simple too (not excusable, just simple lol). I just wanted to fit in with my friends, man..
About my friends and this one time I picked on a kid
See, my friends and I were all cool and we had our shared interests and stuff, and soon enough, I became one of them. They had friends they had history with from a different elementary school, and they pick on 'em every so often for fun. Just teasing. I joined them after I got the gist of everything they were saying and they were cool with it. That attitude of "See? Even he gets why you suck at skateboarding or whatever" was very much a thing between everyone starting to include me into the group. It was super reassuring, and I developed a neat friendship with them as a result. Is that teasing considered bullying? I dunno, it's kinda subjective.
But speaking of teasing somebody, I specifically remember this one guy who had recently moved schools at the time, and we didn't think much of him at first. But come to find out, he was a teacher's pet and a bit of snitch, and not only that, but.. he was fat and slightly uncool.. (Valid reasons to pick on a kid, I know lol) He's that one guy, you know the one, "But teacher! You forgot to give us homework!"
My friends couldn't stand it, but they would've never gone out of their way to outright pick on him unless they were.. provoked or bored and in need of a laugh, I guess. I didn't care all that much about him tbh but fast forward to drama class (yeah, super ironic, I know) and we had to do a group activity. Guess who we got in a group with?? I'm don't remember what triggered it, but everyone at the table started ganging up on him. I played a part in it too, bc I just had to fit in. He.. uhh.. he cried, and told the teacher, and we got sent to the office. All my friends (about 6 or 7) got suspended for a few days except for me and one other. Either they knew we weren't bad kids or the kid told 'em we didn't say as much about him. We were let go, and we went back to class.
In any case! We never picked on him again, we all kinda decided on that, based on it not being worth falling behind in schoolwork. I could dance around it all I want, the fact is we were bullies in that moment, and we may have been an awful part of middle school for him. I'd like to think that if I could meet him again and apologize, that like.. maybe we'd be cool, but I don't know. I don't get to know. Maybe he's holding a lifelong grudge, or maybe he's moved on altogether. I just hope he's doing well and living a full life at this point. Frankly speaking, he was a really nice kid, and I hope he didn't have to face that again after all the mean stuff we said.
I can tell you for a fact that what people consider bullying varies, so in that sense.. it's super dependent on the two parties involved, the bullies and the victims. One could see it as teasing or just playing around, but the other can see it as bullying and torment. One could even be aware of the mean stuff they're doing, and the other could still see them as friends!
Hell, I had what felt like a toxic as hell friendship in high school which was a part of the reason I dropped out. He just liked being rough with his friends.. dudes being dudes, bros being bros, all that. But I felt like it was abusive, and I hated it. I even went as far as starting to avoid him before a class we had together started. After I dropped out, and got in touch with him on Facebook a few years later, he still treated me as a normal friend and he seemed to have mellowed out too so.. I mean.. I don't know if it's bullying since that's the reaction I had, but I also don't know if it could've been avoided had I said something. Doesn't matter, I don't care anymore lol we're good now
I'll say this much based on my experiences being on both sides, I genuinely don't think there's that many people who bully others based on some trauma or some sad home life. I feel like it's more in line with people that don't realize what they do can be hurtful. As a result of believing that, I kinda live my life on the internet writing every single comment I make like as neutral or positive as possible~