If bullying was a civil interaction, independence would be rewarded instead of having attack as a consequence. Bullying is as capricious and surprising as the bully's personality is unpredictable. Others quit after being driven out. Public actions not only humiliate the Target but serve notice to the group that anyone could next fall into the predator's crosshairs. Privacy enables deniability.
Targets are a diverse group of normal, talented people.
Bullying devastates the Target's emotional stability and can last a long time. Those who completed the Aftermath survey were evenly divided into two groups. The shorter-term group was removed from their bullies for one year or less. This alone is horrific. Freedom from bullying is obviously difficult to achieve once wounded.