It's also a bit overblown. If you could rig a war, you would stand to make a lot more money playing the stock market than small potatoes prediction markets. A lot of money has been on the line based on which party wins elections even before prediction markets existed (see fracking or pipeline project approval as obvious examples).

This is an absolutely idiotic proposition. What does it even mean to "rig a real world event"? This is complete nonsense. Either you can influence an event, or you cannot. If you can, then there usually are multiple ways to gain from that, one of which is, yes, betting. You can wager a friend that he won't dare to do something, and if he is intending to do that, he might accept. It happens daily, always did, always will. It is completely normal. You don't need Polymarket for that. In fact, you don't want Polymarket for that, because for your wager to work like a "payment" for doing something questionable you don't want there to be any bidders other than the one who can influence an event, and people who want to bribe him. Because bets don't work like bribes: you only gain proportional to how much you bet + odds.

When you are betting privately with your friends, you can decide odds arbitrarily, so it can be more like a bribe than a bet (but then you don't really need to frame it like a bet). When you are betting on sports events with some bookmaker, it has to be more fair, because after all the bookmaker has to balance bets against money flow. But still, it is completely opaque, and in the end bookmaker can set odds however he likes, he may reject any bets he doesn't like, basically, he can do anything, which is to say he can play unfairly, which is the only thing real gamblers are worried about, and which basically all bookmakers do. Previously, betting was an unfair game.

The only thing that Polymarket and the likes changed: they actually made it fair. Odds are only based on how much money each side bets. The middleman only gets commission. You won't be banned for actually being better at predicting events than other people are (which is almost unheard of with traditional bookmakers, because they won't tolerate good betters). This really is a good thing.

For purposes of rigging anything this is in every way worse, than all existing alternatives. If you can influence the event, you still cannot gain any other way than betting on the outcome you are set to achieve. And unlike when wagering with your friend, it has to be a real bet: you will only get more than what you bet proportional to the general belief of the market. Well, for someone poorly connected there is additional benefit, that you now can actually find a friend to bet against. But, let's be real, if you are a person who can personally decide an outcome of an event big enough to get traction on Polymarket, you probably aren't a guy who has any problems with that. I'm pretty sure you could find a couple of guys who are not only ready to bet, but are probably ready to make a hefty donation in Monero to swing it one way or another.

(Also, it really has nothing to do with the heart of the argument, but I just cannot ignore that: one must be completely delusional and ignorant about the real world to think that previously wars were started for some other reason than money, and that now things suddenly change because of Polymarket.)