In general, his life story is the perfect argument for intelligence alone not counting for much. By most conventional standards, he is a failure, since he has failed to find satisfaction and success professionally and has never made use of his gifts. He seems to dedicate most of his effort and thought to a crackpot "theory of everything", something which the world does not need and which no one is interested in (however, his choice to do this interests me because it's so cliche: the crazed scholar working day and night on fatally flawed work, just like Casaubon in Eliot's novel Middlemarch). The remainder of his time seems to be spent socializing with the "high IQ community" (which are almost all a bunch of really weird, broken people in my experience: functional very intelligent people have better things to do with their time).
I was intrigued, so I watched an in-depth interview with him (done by documentarian Errol Norris, via YouTube here, here and here). The interview makes it very clear WHY he has failed.
He is obviously highly intelligent and equally obviously highly psychologically damaged. For example, when recounting his shockingly abusive childhood (stepfather chained him to a wild horse, which soon bolted and dragged him for several miles through barbed wire until the chain broke; he says he was constantly covered in welts and bruises), he is calm and even smiles grimly, as if it was a rather humorous memory. This is someone who's never come to terms with what happened or faced up to his own feelings about it.
Later the interviewer gently suggests that his very odd choice of violent, physically damaging professions (like being a bouncer, which means fighting with violent drunks on a regular basis) might be related to his past. Langan completely denies this and seems befuddled by the idea. Of course the interviewer is right: Langan is both recreating the world he's familiar with (violent interactions with his drunken stepfather) and deliberately injuring himself (probably because he feels that he deserves it). A certain reluctance to truly challenge himself mentally is probably also involved, because then he might have to face the fact that he might not be the smartest, and that seems to be one of his main sources of self esteem. Note that he prefers to "study" something vague and non-measurable: that way, no one can really tell him he's wrong and his work is bad.