What makes narcissistic parents leave?

I have children with my ex, and often feel that he only takes them for visitation as revenge towards me - that it is about 'taking them away from me' more than being a parent for them. I do also think that he gets a narcissistic high from others who tell think it's great that he's a dad, and that may play a part too.

For those who have kids with an ex-narc, and have seen the narcissist leave the picture - what do you think was the catalyst? In my gut, and given how consistently narcissists, sociopaths and pyschopaths behave in other ways - it seems like there would be a common denominator in this way as well.

fyi - I do understand that limited contact works well and have been practicing that for 2 years. I have also done regular CBT therapy, as well as Theta healing - lots of deep introspective work to understand the beliefs in me which would have attracted this into my life.

Peace and strength to all :)