Back to the beginning of the accident maneuver: there was an additional gate besides the speed (very important) and altitude (in my opinion, not so important because one should fly a loop so as to be able to come out of it above the starting altitude; you then finesse the pull out to come down to the height above ground desired at its completion), That third gate is the point at which to begin the bent loop so as to come out on a line parallel to the show line. He may have begun the pull up late since it appears that he wasn't far enough west as he was coming down its back side. If on the run-in, he realized that he was past the point where he should have started up, he may have glanced at the airspeed indicator and decided, as hard as it is to believe, that he was going fast enough to begin the maneuver.