I don't think this event is supposed to deter gambling bookies and casinos from providing markets for people to bet on political events, to be honest. In the end, if people really want to bet on these things, they will always find a way to do so.
It is reasonable to think they actually violated the law of the United States, by willingly allowing people from the country to bet on those markets and not having an enforcement mechanism to avoid those using VPN to place their wager.

Though, the fact the webpage accurately predicted the winner and the political implications of the change of government in the USA are big enough to assume there is a little bit of a vendetta in this search warrant on Poly market. The political left is still hurt and feel greatly humiliated by Trump's victory, there is no doubt about it, I think.