I think narcissists are quite a lot more complicated than people on here give them credit for being. They're very damaged people and a lot of their behaviours are toxic, but they often also have good qualities and I do think they feel what they think is love, at some point, anyway. I don't think that in the early 'love-bombing' stages of the relationship they are consciously manipulating their partner. They're literally delusional themselves, and simply overlooking/ignoring anything that doesn't fit with their fantasy vision of themselves or the other person.
When they copy all your good qualities and act like your perfect match, I think they're not really aware they're mimicking and acting. Like if you have a dog you really love, they kind of get caught up in your enthusiasm and feel as though they really love the dog too and suddenly feel like having a dog is something they've been missing out on. So they might say things like "I've always wanted a dog but my ex didn't like animals". The thing about the ex may or may not be true - they may have never even talked about getting a pet with their ex - but I don't think they're saying it maliciously as much as they're just creating a plausible excuse why they never got a dog before if they "always wanted one". I don't think they really think too much about anything they say or do - it's all shallow-rooted.
Of course, as time wears on and the dog needs walking every day rain or shine and the dog gets sick and needs expensive medication at the same time as your narcissist wants to buy himself a new watch, this initial shallow burst of enthusiasm wears off and the narcissist starts to see the dog as a burden rather than a pleasure. There was never any real, enduring love there to start with so when times get tough, they tap out.
That doesn't mean that the afternoons in the early days when you would take the dog to the beach and throw the ball around and your narcissist would wrestle with the dog and call him the 'best dog ever' didn't contain some real pleasure. It's just that the narcissist can only maintain good or loving feelings during the good times.
During times where they have to make sacrifices, do things that serve others rather than themselves, apologise for their actions or wrestle with the uncomfortable understanding that other people don't think of them as flawless and have different opinions and desires to them, they simply can't handle not having things exactly their own way. They are like little children stamping their feet and saying it's NOT FAIR that they can't have the icecream and they don't WANT to go to school and they HATE YOU YOU'RE THE WORST because you want them to put their shoes away or say sorry for drawing on the walls.
Little children learn and grow out of this phase when they're nurtured and supported by a good-enough parent. Narcissists typically haven't been given that (or they've had the opposite - a pushover parent who never said no), and as adults, they have learned to use bullying and manipulation to get their way.
They carry a deep sense of deprivation and entitlement to do whatever they want because they were denied that love, nurture and gentle coaching to develop self-discipline and empathy in childhood and carry a deep resentment towards others. It's tempting to think that you can 'love them out of this' by giving that kind of love now, but the reality is that it needs to come from a therapist who can become a substitute parent figure to them, not a partner. A therapist doesn't rely on the narcissist for anything so doesn't get emotionally involved with them. It doesn't work the same way in a relationship, especially because narcissistic relationships generally become deeply enmeshed very quickly due to the love-bombing.