Question about NPD

So I've been reading that narcissists are very insecure and feel unloved...how can they feel this if they had a woman who showered them with attention, always wanted to be around them, and loved them unconditionally? A person who told them how much they loved them? A person who stuck by them through and through? That I don't understand...my EX narc, told me he wanted to have children and get married...but he never took the steps to propose after 8 yrs together...instead he was to busy saying he was faithful but going to online dating websites and meeting women there...and he even left me for a woman he met online who lives 1300 miles away who has children of her own and is 40 so she's not going to have more children and get married again probably...I'm 30 never had children or married and used to live with him? We broke up because I believe he knew I was on to his games and that I wasn't letting up...IM NOT SAID ANYMORE I AM SOOOOOO THANKFUL IT'S OVER!!!! But I just wonder why they say they want to get married and have kids, yet have affairs with women that didn't know he was in a relationship...and why break it off for a woman who lives so far away, has children, and who can never move close to him bc she obviously shares custody with her husband who lives in her state...this poor woman never knew I existed..so how could he believe that he would actually have a good relationship or a long and healthy one with a women who he knows that he has been lying to her for almost two years?? I will never ever get back with him bc I know my value but I just wonder sometimes what these people are thinking!!! Also he's in his late 30s and if he wanted children why would he want to start a new relationship, have to go through the courting period, and with a woman who is clearly not gain to have more children? Do NPD ever have the ability to love truly and deeply? How could you love someone who you have been lying to for 2 years?