Metaphors can help us to understand the deeper dynamics:

A bully is like a mosquito

Like mosquitoes bullies sense out their targets, choose one and 'feed off' it. After a few days (for bullies it may be longer), they need to feed again. Another victim will be found to satisfy a bully's insecurities.

A bully is like a praying mantis

A praying mantis stalks its victim, often spying on it before attacking. Likewise bullies watch and monitor potential victims, testing them to see how they react. The praying mantis seizes its prey in a vice-like grip and eats it alive (it may feel like that to a workplace victim too). Once bullying begins the victim becomes trapped. Often support, from colleagues and friends, is needed for the victim to stand up and challenge the bully or escape from the situation. However work colleagues and managers may turn a 'blind eye'. (According to superstition the praying mantis creates blindness in others). Victims become socially isolated and more vulnerable unless changes are made to the interpersonal relationships and group dynamics.

A bully is like an addict

Bullying in the workplace is like an addiction. The underlying cravings are similar to those of other addictions i.e. the needs are insatiable. Bullies are rarely satisfied with one victim. Many are serial bullies. They use and abuse victims and when they are of no further use to them dispose of them and hunt out others to feed their habits.  

A bully is like a Jekyll and Hyde character.

Unpredictable and two faced. Bullies can be charming to some individuals and evil to others. This reflects a splitting within the psyche into good and bad - a defence against anxiety.

Victims in research studies, have likened themselves to slaves, prisoners and heartbroken lovers. These metaphors portray their lack of agency and control over their lives and inability to take charge.