My theory is that we have only so much Regard in our psyches. As Regard goes higher and higher, there’s simply less and less available to dole out to other people. This theory works well for low self-esteem as such folks often seem to have extreme regard and caring about and for others. That is because they have little love for themselves, so they have a huge excess love or regard supply that wants objects to focus on. So that love inside of them goes out into the world and attaches to other humans.
It is quite amazing how much love for other people some people with low self-esteem have. Saints are called that for a reason. I would assume that as self-regard goes higher, one simply starts using up their Love supplies or Regard supplies. We only have so much love or regard inside of us, we are not bottomless pits of sugar and spice and everything nice. As more and more your internal love is committed to the self, perhaps there is less and less to give out to others. Hence you have the NPD person who loves himself but cares little or nothing about others. Here is where the narcissistic abuse enters in.