I haven't seen the doc yet, so maybe it will change my mind, but I think Te'o was in on it in some way. There is just no way a reasonably good-looking, elite, well-known football player for Notre freaking Dame was genuinely fooled by someone impersonating a girl online. It isn't like he had limited options. Usually, people who get duped by that sort of thing are really young and impressionable, or really naive, socially awkward outcast types. At the very least, he was being disingenuous about the relationship he had with "Lennay Kekua" - their relationship was entirely online/he had never met her, but he neglected to mention that. He also had received a phone call from the woman he knew as Lennay Kekua, saying that she was still alive, but he kept talking about her death to the media for weeks after that.
Perhaps he was genuinely catfished initially, and then by the time he figured out he had been tricked, the media knew about his "girlfriend" so he went along with it to avoid embarrassment. Regardless, somebody other than the guy pulling the hoax knew what was going on and gave an anonymous tip to Deadspin.