You hit it on the nail head with lack of coping skills. I had a grandmother who tried to compensate for the way my mother treated me by treating me like I was royalty. And my coping mechanism for being treated poorly at home was thinking that I was better than everybody else in some way. Combine those two
with the fact that I was taught no coping skills, and yes I became a narcissist.
When I had my awakening, I was finally able to put to work some coping skills I learned the hard way, in a mental hospital. But once I realized the problem was me, the changes were instant. I was ready for change.
Unfortunately, some people have no such awakening. And I avoid those types of people like the plague.