Bullying has many untold factors as to why people do it.
Many students have had some occasional bullying in any given school term.
There are many reasons and possibilities as to why people bully, most of the time it's because the victim is different in some way.
Other reasons are:
Someone's appearance (e.g. hair colour or style, height)
Both males and females are capable of carrying out a vicious attack such as bullying on others.
Some bullies only do it to uphold their reputation and look “hard”.
Another reason would be either sex of a bully trying to maintain their superficial superiority.
Many bullies only bully others out of jealousy and many of the people who have been bullied go on to do great things with their life, like some famous people who have been bullied.