In late 2016, federal agents showed up at the Fort Myers, Florida, homes of brothers Brian and Edward Krassenstein, seizing computers and financial records, and hauling off with “at least 20 to 30 bundles of stuff.” At the time, the story was just a notable blip on local media’s crime blotter. But in the two years since, the Krassensteins have become more than a pair of local businessmen. They’re now prominent members of the online anti-Trump “resistance.” According to the feds, they also, until recently, ran websites that propped up fraudulent online financial scams. Law-enforcement officials last year seized nearly...