You're conflating insider trading and blatant corruption.

Imagine if a CEO of a company does something that would damage the price of the stock of it's own company, having shorted the stock before? That's not insider trading, that's (probably, I don't know the exact term) fraud and will lead to prison sentence.

Prediction markets enable the policymakers to make these bets. Arguably, there should probably be sorts of limit on who is allowed to be there. But there are still counter examples like Nancy Pelosi who somehow manages to go around these limitations in stock market.

That's whats currently happening.