he has mentioned first so it might not be deliberate on his part
This is probadly because he is intelligent. I had this with Ex H, he agreed with me on everything so once I deliberately forced him to make a choice on a preference and he came up with the same idea as me. It confirmed in my mind we were obviously "soul mates", and I honestly thought we were meant for each other (although he had been married before).
Later after marriage we barely agreed on anything and I realised he had learned my cues, in the same way profiling works. If you want to hook someone it's actually not that difficult.
I would happily say I was naive because like the OP, she knows something is off and may choose to ignore it.
However I didn't know what I was dealing with and that was due to lack of knowledge so I think naive and uneducated is valid.
Op, the "why" is what keeps people hooked in bad relationships because it doesn't make sense. Even now I sometimes struggle with it but I do accept it is a personality trait and can't be changed. I suspect science in 50 years will offer
explanations but for now we need to accept it's a brain wiring issue, most likely in the cerebral cortex region. Studies have shown it is also increasing so the chances of meeting an NPD partner is higher.
NPD thrives because when we assess other people we use ourselves as a yardstick and tend to project our own emotional state and values onto others but some people are just egocentric and lack empathy. The juror is out on the cause but genetics is also a factor as well as environment.
If he is narcisstic then he is pursuing you for something..status, money, access, as well as "supply". For a person with NPD supply is vital as without it they feel empty which is why they are often never single for long and why they have affairs as they need to line up someone.
In my case, some of Exs behaviours were instinctive as opposed to premeditated as he sees the world differently than I do. For him it is a case of "control or be controlled".