With its streamlined curves and glow-in-the-dark sound system, the silver Lamborghini Huracán Performante was the stuff of teenage fantasy: $350,000 of aerodynamic metals and lightweight upholstery, packed into a taut and powerful body. Ben Armstrong loved it dearly.

When he started shopping for a Lamborghini, Mr. Armstrong, a cryptocurrency evangelist

As the Lamborghini was lowered from a delivery truck, Mr. Armstrong, better known by the nom de crypto BitBoy, let out a joyful laugh. “I may have shed a tear,” he said at the time.

Back then, BitBoy was one of the most popular figures in the wild, scam-ridden world of crypto influencers. Cultivating a persona as a straight-talking everyman, he filmed a livestream five days a week in which he lectured his hundreds of thousands of listeners on the virtues of experimental coins with names like Polkadot or XRP. He said that regulators were fools, and that digital money offered a path to upward mobility. The Lamborghini was vivid proof: Crypto would make you rich and cool and successful.

Two years later, Mr. Armstrong, 41, has lost his production company and much of his wealth. His friends have turned on him, and his wife has filed for divorce. Over the last five months, across countless social media posts and videos, Mr. Armstrong has claimed to be the victim of a “criminal conspiracy” by “terrorists” who took over his YouTube channel. “BitBoy is dead,” he recently declared.