From my reading, these betting markets have recently tracked as well as 538 long term, so that's a decent outcome. I wonder if they just swing to vendors like 538 to look for "an inside track" to bet against overall, but it's a small system so it's not clear.

The issues they have are being largely illegal or grey market in the US, which limits who will interact with them. There very well could be experts who could "make money" that won't do so because of their current status.

They also appear to be very erratic in the short term, the same way a lot of sports betting and stock gambling is. Single events can send the numbers into tailspins. We've had some pretty intense recent events, so I'm not exactly confident in their choices.

I'd say lastly that they are heavily right wing or right wing adjacent spaces. Some people are just there to make money, but others are tossing it away on ideology, especially in these divisive times. Markets aren't always rational actors, they just tend to be in aggregate.