PI is really a brilliant movie -- filmed like a documentary but it's actually very cleverly scripted. The hero is also the "villain." The threat of the superman (Ferrigno) is juxtaposed with the fact that he's psychologically frail. (Lou was actually surprised when he saw the film, no knowing they were going to play up that angle). Originally it was to be about an underdog from nowhere toppling the king. Arnold was set to retire. But his ego made him train harder and his charisma was so strong that the producers decided to make him into this unstoppable machine. The subplot with Waller and Mike Katz was scripted. There's even a "third act surprise" which is standard script writing. That's when Serge Nubret shows up.
People complain that it should have had more bodybuilders of the time but they don't understand. It wasn't about bodybuilders. It was about competition. Bodybuilding was just the backdrop. It's an amazing picture and the game was irrevocably changed forever.