Why doesn’t the Narcissist give closure or break up in a civil way, how can they be so evil and discard, ghost you like yesterday’s chewing gum.
I would say their lack of empathy for other humans is what feels so evil. Narcissists focus on their needs and desires.
When they discard you, your pain is either of zero concern to them, or if they are higher up on the spectrum then they can get off on your pain, your suffering offers them supply. It makes them feel powerful to control another human through emotions, even if they discarded you.
Once we take our power back and heal, why they did or did not do things will be irrelevant to our life. Stay present. You did not survive a narcissistic relationship to suffer in your thoughts and emotions once you were free of their grip. Take care of yourself and focus on your healing.