I think it could be one of many causes of asexuality.
If you see it from whom you "like", you like nobody but yourself (which would rather be egosexual, why isn't that a term?).
If you see it from the opposite side, you see different things. A person can dislike the opposite sex in the same way gays do, but they also dislike the same sex in the way a straight person does. That way, there is simply no one left to like.
Also, I think you can tell a lot if a person is both aromantic and asexual. Some people are not aromantic but are asexual, they might have sex just to preserve the relationship or they date another asexual. Being that way, I think something other than narcissism caused that.
I think with a true narc asexuality, you have a really strong aromantic side. It's just a theory, so if you can tear it down or add to it, feel free.
I'm not here tip tear anything down. I strongly think that our natural survival instincts give us a desire to breed and pass or genes down the line. So it is essentially de-evolution to become gay. It is a "fluke" it may either be some sort of chemical imbalance, or a mental imbalance. Desiring men is a female trait, a strong desire for men would make a female more likely to bear children. But maybe something gets mixed up and female features end up in a male body.