A narcissist is a person who by definition has never felt loved.
This may seem counterintuitive, but I think it is true.
What narcissists do is interact with themselves, using other people as proxies to hold their delusions about themselves. Every conversation is a monologue, but it is vitally important for a physical person to be there to sustain the illusion.
Narcissistic supply, then, is really the fuel that sustains their defensive insularity. In effect, it helps them protect themselves from themselves, because there is no solitude like a narcissistic solitude. Such people are alone with others; and much more alone when actually alone.
I’ve been playing with all this for the past week or so. I haven’t quite figured it out, but this is a progress of sorts.