Why is he a loner here?

Usually loners are alone for good reasons, or at least reasons that they feel are good enough to avoid as much interaction as possible. He may feel annoyed by other people, because of how "brilliant" he may be. He sounds like the kind of guy that appreciates the quiet, or a deep thought. So maybe if you want to talk with him, try not to be overbearing, for he may find you a bit of a pest if you talk too much or too soon. Instead, try to talk about things that spark his interest, for if he feels he's comfortable enough for you to listen to his views, he may feel comfortable with talking to you normally.