That's a very strange account of how bullying works. The impression I get from what people tell me and situations I have witnessed is that the lonely male bully described here is a very rare exception.
The typical situation is a group of people led by a smaller sub-group acting against an individual in pretty obvious ways. The victim is sidelined and ridiculed openly so everybody knows. Teachers always know.
The authors describe the bully as some kind of genius who always selects the right victims and always chooses occasions wisely. That's complete nonsense.
People who become victims are completely random. Take any closed situation where people can't leave at will, like schools, military camps, prisons, the workplace, and anyone can be made a victim. No need for the bullies to choose wisely.
There's just no way anyone can defend himself against a socially dominant group who decides to bully them. The only right way to react is to leave instantly. Victims can be harmed for life if left in a situation like that. That's what I learned from someone very close to me who was a victim of bullying and researched the whole thing extensively later.
If you have kids who are being bullied, just take them away from the bullies immediately!