"You were interested when you saw her picture + You were excited to go on a blind date with her." Because usually in Korea before 소개팅 you share each others photos and basic information, the guy was probably interested in the girl even before he met her but after their first date he thought she was too 사차원 and wasn't into her anymore. The guy is talking about it to his friend after the blind date and his friend is curious because he thought the guy liked her. :)

왜? (니가 그여자를) 예쁘다고(말하고) 좋아하면서 (그 소개해주는 장소에) 나갔잖아 Maybe he already saw the girl's photo...