Some have grown up in narcissistic homes where love was conditional so therefore the only love they knew was if you do for me, if you behave this way, if you get these grades, if you make the parent look good by your achievements, if you lose your identity and not voice your opinions or needs, if you become a living and breathing robot with stuffed emotions then you are loved.
They can either fit into the scapegoat or golden child roll depending upon their performance. Others have been emotionally neglected and shunned in their own household as if they don't exist. So those with rage use it to control their environment just like the parent would have. The narcissist controls others by their moods. I believe they are intentionally doing this so others take on the guilt, shame or blame of the narcissist. It is a form of punishment, treating a person like they are "bad" and deserve their ill treatment. It's one of their forms of manipulation. This way the person they are targeting never feels they are good enough to please them or warrant their love and acceptance. This makes their target feel like they have to do more to make the narcissist happy. They take on the guilt of not doing enough, not being enough, not saying just the right things at the right time so the narcissist won't explode. The narcissist then accomplishes what they have set out to do which is to make the person feel worthless, helpless and responsible for making the narcissist perpetually happy. You end up losing yourself while they gain continuous supply.
It's never going to be enough for the narcissist because they are like dry bottomless wells. They can't see it in themselves so they seek after others who will let them drain every ounce of your soul until you feel as hollow as they are. Most who have big hearts end up with narcissist's because the narcissist can spot an overflowing well for consistent supply.