I have wondered this exact same thing, I was with a narcissist for ten months up until 3 years ago. At first, I thought I'd hit the jackpot, he was everything I ever wanted, plus amazing sex. I absolutely adored him and we had a fantastic relationship. I am an extremely strong-minded and stubborn woman and I think he struggled with that because I didn't knuckle down as I guess many other women had, and I was obviously a huge challenge. We rowed like nothing on earth, they were awful, but gradually I did start to apologise for things that weren't my fault, I did become a little bit controlled, and it was a hugely awful and stressful time, but the beautiful times still outweighed the bad.
When I eventually ended it, he started to stalk me, first in a love bombing type of way, then in a nasty, vile shouting at me in public and cornering me in the woods when I was walking the dog. I had to have him arrested in the end, but he carried on but n weird ways that, when I told the police, I realise now I sounded like a mad woman. He'd also done the same to his ex-wife. I was on anti-depressants for a short period and had four sessions of counselling which really helped me, and I eventually got over him.
We live in a small town, hence the impossibility of completely avoiding him, and weirdly we have become friends again, which we were before going into the relationship. He's coming over tonight to fit my new blinds. However, he still makes odd comments, little unimportant things, like he doesn't like my skimmed milk. So I tell him if he doesn't like it, he can fuck off and not bother coming again. He laughs. I think if you can recognise and shut down the crap, it's a lot easier, but god, it's exhausting.
In answer to your question, I do believe he loved me totally, but his need for control and dependency outweighed the happiness we did have in each other, and I think it's actually impossible for him to be truly happy because he's too busy looking for that control.