I don't understand the connection you make between being intelligent and not that interested in being social, and not being social and not happy.
I disagree.
I have a high IQ - among the 1% of the population when I lived in Denmark. I'm not very social and never have been. But I'm VERY happy. I have a "job" I love (being an independent writer). I live the best place in the world. I have a wonderful family. I'm happy, but yes, I don't socialize much.