While most of Donald Trump’s allies braced for the release on Thursday of Special Counsel Robert Mueller’s report, believers in the pro-Trump QAnon conspiracy theory approached the long-awaited publication with a sense of thrill. For years, QAnon fans have been mocked for believing that Mueller was secretly in league with the president, working hand-in-hand to uncover Satanic rituals committed by top Democrats before shipping them off to Guantanamo Bay. They had been told it was ridiculous to base their entire political worldview on a series of anonymous clues posted on internet message boards — including one that claimed Hillary Clinton...