Narcissists are incapable of true love and genuine intimacy. They only love themselves, and surround themselves with, or rather they catch in their web, people who can reflect their own greatness back to them. Narcissists are addicted to the six As we call narcissistic supply (NS): attention, acceptance, affirmation, affection, admiration, and adulation. Most people need healthy amounts of all these, but for the narcissist they are the lifeblood of their existence. So they find people who will maintain a constant flow of NS. If a narcissist can no longer extract NS from her prey, she will act badly like a neglected child to get negative NS, because they often receive the same gratifying feelings by knowing they can make you angry or frustrated.
In short, there are two kinds of people in a narcissist's life; those who see behind their mask but stay because they are stuck in the web, and those who don't see behind the mask (narcs are often very charming and successful) and continue the flow of NS.
But narcissists are shameless, and if you refuse them their needed NS they will devalue and discard you (and probably go on a smear campaign to denigrate you to others).
The other key thing for people to understand is that narcissists target the very people who possess the qualities they themselves don't have: empathy, capacity for forgiveness and intimacy (more than just love-bombing), ability for remorse and regret and repentance, and the openness to be genuinely interested in something besides oneself.
We need to teach our children how to spot narcissists so that they can be inoculated against their toxicity, but also, and perhaps more importantly, we need to raise children who aren't narcissists by nourishing their empathy and stemming their monstrously malignant self-absorbed selves.