Belgian police swooped across Brussels, the European Union’s seat of government, in early December, raiding offices and apartments, and seizing €1.5 million in cash—money that prosecutors claim was bribes from “a Gulf state” widely thought to be Qatar, given in exchange for favorable decisions in the 27-nation EU Parliament, in the run-up to the World Cup. The so-called “Qatargate” scandal left Europe’s politicians reeling as it shook the bloc’s foundation. “European democracy is under attack,” warned EU Parliament President Roberta Metsola, while European Commission President Ursula von der Leyen fretted that “corruption like that erodes the trust of the public...