I believe that what happens is that a person who may have had abusive parents has had to learn how to cope with that, because as a child they cannot leave. So they are forced to be tolerant of people who are abusive.

Then when they get older, a self-centered person who just wants to use other people can easily spot someone who is "useable". And at the same time, the person who has learned to tolerate abusive self-centered people will naturally tend to want to be "nice" to an abusive person... because it is a learned behaviour.

In fact, I even had a person tell me as much, when he said "He knows that you are the only one who will put up with him". It is sort of a mutual sickness. People with Narcissistic Personality Disorder may have had parents or at least one parent who tolerated their temper tantrums or other selfish behaviour when they were children and so they grew up thinking that everyone ought to treat them that way. So they unconsciously 'seek out' people who will tolerate them. While at the same time, their victims have learned to be tolerant because their own parents were abusive.

...at least this is what I have experience. They usually search for someone who is easy to take advantage of and actually place themselves in such situations. For instance, I have discovered that many people with NPD tend to flock to the Internet on forums where nobody will know who they really are and what they are really like. Lots of times, they will choose Christian Forums because they realize that Christians will be more likely to be tolerant of them. And its easier to disguise your true behaviour on a forum where they are relatively anonymous. And so, it may not actually be that people are attracted to these people with NPD, it may many times be that these people with NPD place themselves unconsciously in places and situations where tolerant victims are plenteous.