This is called a crush, or infatuation. It will disappear, as this is literally the only time you've spoken to him outside your one night hook-up. Don't kick yourself on it and get mad. You went in knowing the rules you BOTH set for yourself. Best is to just let it go, seriously.

Honestly I think you just felt more attraction and probably enjoyed the sex. Then afterwards you learned he was a smart person. That’s great but I don’t think after a one nightstand and a conversation you have true feelings. Maybe try and hookup again? But I wouldn’t push it on a relationship

This is one of risks of casual sexual relationships. As human beings, we have a tendency to “catch feelings” for someone we have been intimate with. Some people don’t feel this either because they are jaded by the frequency of these couplings, or they carefully guard their feelings, or they have sociopathic tendencies. Let this be a learning experience for you. Either make casual sexual experiences more rare unless you feel the possibility of chemistry between yourself and your partner, or guard your feelings more carefully if this is going to be something you do.

And that's why I don't do "hook ups." Too many stories like this one.

that was the story of my life before I met my husband. I feel your pain, OP ❤❤❤❤

Catching the feels is the worst STD.

That'll happen.

rule #1 No conversations

Never chill with your bootycall

And that’s on treating the best thing life has to offer as a casual thing