Seeing all rules and norms as mere facades for a vast conspiracy also legitimizes getting around them to exercise unlimited corruption. The cynicism implicit in conspiratorial thinking frees you up to indulge in anything you want. Mr. Trump was, like many American businessmen, attracted to Russia in the 1990s and early 2000s, a time when rules — both logical and financial — were suspended. Throwing off the constraints of factuality goes together with throwing off political and legal norms, which for Mr. Trump means, among other things, turning his private lawyer, Rudolph Giuliani, into a private diplomat.

There’s a dark joy in being released from the constraints of legality and factuality, something Mr. Putin grasps well. When the Russian president went on international TV during the annexation of Crimea to smirk and say that there were no Russian soldiers on the peninsula, and that the soldiers the world could see were just locals who had bought Russian military uniforms, he wasn’t so much lying as demonstrating that he doesn’t care at all about facts and, by extension, the rules governing his behavior.

Mr. Trump, too, has doubled down since it was revealed he was exerting his own pressure on Ukraine. Despite all the protestations of State Department officials and Ukrainian journalists who painstakingly show that the accusations that Joe Biden helped fire a Ukrainian prosecutor to protect his son are specious, Mr. Trump and his allies have responded by repeating them. The president even suggested that Mr. Biden should be investigated for alleged corruption in China, too.

Mr. Giuliani has gone on cable news to spin an ever-greater web of insinuation, dropping in dark questions about whether Hillary Clinton’s email server might be in Ukraine or why Mr. Trump’s 2016 campaign manager Paul Manafort was jailed because of evidence of his financial impropriety there. Watching clips of Mr. Giuliani, I am reminded of the catchphrase of Russia’s most prominent current affairs TV host as he twirls from one conspiracy to another: “A coincidence? I don’t think so.”

This attitude is what makes Kremlin propaganda today different from its Soviet predecessor. The Soviets tried to make their lies sound factual. Even their disinformation in the West was meant to feel foolproof: For example, the 1980s campaign to show that the C.I.A. had invented AIDS was carefully curated through Soviet-controlled medical conferences. When President Ronald Reagan called out the Soviet leader Mikhail Gorbachev, Mr. Gorbachev feigned horror at the idea that the Soviet Union would stoop to lies. Today, when the Kremlin pushes conspiracies claiming Americans invented Ebola or Zika, these stories are thrown online with no serious attempt to make them sound believable. Their aim is as much to confuse as to convince. And there’s no shame in being caught lying.