I think adult bullies are a part of the problem that spawns youth bullies.
Its the same situation that gets played out all the time. Power hierarchies turn into totem poles where everyone dominates the one below them. The boss yells at the working man, who goes home and hits his wife, she screams at the kid, and the kid kicks the dog.
Being dominated gives you a sense of weakness and frustration that you aren’t able to stop it. Some people self-destruct and just get really depressed and focus their anger internally (maybe those who cut could be lumped in here). Others take their anger out on someone else and try to make themselves feel better (and more powerful) by dominating someone else.
So bullies are frustrated that they have no control over their lives, their dad or teachers boss them around and dominate them. So they dominate their classmates. What I noticed at least in middle school was it wasn’t just the bullies and the rest of us, but there was a pecking order. I suppose I was in the middle of that scheme. Bullies picked on me, and I picked on other people. So I guess that made me a bully. Yet I was also a victim. And the people who picked on me were also victims.
But yes, there is indeed bullying in the adult world. Its just more sinister and… adult. No one is going to stick your head in the toilet, but there are many other ways of more subtle ways of tormenting people at the office. Anyone who bosses around youth are bullies. Exactly the same dynamic. Indeed that’s what starts the bullying machine moving in the first place in my opinion.
Independent of this youth rights/hierarchical analysis I do believe that all humans have the capacity for cruelty. Buried away in them by the moderating effects of civilization and morality (thank God), but still there. Some part of all of us enjoys seeing others in pain. Nietzsche wrote about it. So some part of this issue is individuals with poor impulse control not suppressing their desire to be cruel to others.
These are the people who only really behave morally because there is a law backed up by force. When the rules disappear and the threat of jail or punishment disappears then they become sadistic bastards. Look at what happens to people in war. Otherwise civilized people back home commit horrific crimes and torture when put in a situation where their behavior is condoned or allowed. Anarchy brings out the horrors of human nature.
So another reason bullies exist is simply that they can get away with it. The school authorities don’t do enough to stop it.