Except, gambling isn't illegal here - in fact, it's very common. There are lots of casinos within a few mins walk in any city in Spain. All the prediction markets need to do is comply with existing laws.

For some reason, American companies have a really hard time following existing laws and regulations here. AirBnb and Uber both had the same approach of basically saying "Oops we didn't know" until the law (and others) cracked down on them, I'm sure someone could find older examples too, and surely tons of examples outside of Spain too.