FWIW I am also unconvinced by the article's thesis that prediction markets "beat" polls. But I'm not sure I agree with your premise that we need to ascribe causality if markets beat polls. The "point" of markets is that they work in mysterious ways: the combination of financial incentives and the wisdom of the crowd coalesce to price things correctly. You might be able to point out why a specific market participant has a specific opinion and makes a specific bet, but doing so for the entire market is a fool's errand.
FWIW I am also unconvinced by the article's thesis that prediction markets "beat" polls. But I'm not sure I agree with your premise that we need to ascribe causality if markets beat polls. The "point" of markets is that they work in mysterious ways: the combination of financial incentives and the wisdom of the crowd coalesce to price things correctly. You might be able to point out why a specific market participant has a specific opinion and makes a specific bet, but doing so for the entire market is a fool's errand.