Interesting theory. I'm inclined to disagree, however. Prediction markets essentially allows people to trade information for money, even the types historically more difficult to trade. There aren't enough people betting on things for deliberate misinformation to become worthwhile, IMO, and most people would stop betting after being in the wrong too often, unlike casinos which always let you win sometimes.
I believe the misinformation is largely by self-interested parties. Politicians as well as influencers trying to push agendas, and the engagement/attention farming for advertising revenue, which are largely indifferent to truth.