I feel like there is two ways to frame this.

The first people betting on the outcome they want vs outcome they think will happen.

I think the second obviously make sense. If you had two experts arguing over how a war would go and they where willing to make a bet on it that is good because they are putting “their money where their mouth is” or have “skin in the game”. That’s a good thing.

The first implies manipulation or just a moralistic problem.

The issue I guess is it’s not possible to have one without the other. But I would guess most people are betting because of the second reason and not the first.