Because he saw the movie thus making him "the audience."
Holy shit, did I just quote a guy that called both himself and ME
BTW, most LOST fans I met (I mean the ones who stuck with the show to the bitter end, and still ferociously defend it) did strike me as pretty stupid, I must admit.
This being said, Damon Lindelof is a hack, a douche and an idiot. IMHO, of course.