There are several reasons why people become targets and they usually have something to do with sex and money, in that order. The targeting may have to do with a messy divorce, child custody, unrequited love, whistle-blowing, revenge, differences in social, political, or religious beliefs, etc.
Targeting for monetary reasons can include anything from denying you social security benefits or workmen's comp. to outright stealing from your bank account, from sexual slavery to embezzelment, and so on.
Targets should vehemently resist all attempts at being denied any and all kinds of government benefits. Appeal any bad decisions and if you don't like the next decision, appeal it again.
Another claim being made and that is that people might be being targeted for experimental reasons by the military or security agencies, usually, to test out how certain mind-control techniques and weapons work, which goes back to money or sexual slavery.
The main purpose of the assaults is to discredit and control targets. Harassment and abuse is often set up by corporations, businesses, organized criminals, street gangs, right-wing extremists, doctors, dentists, lawyers, or anyone who stands a chance of making any money off of targets.