For two decades as the chief executive of the online retailer Overstock.com, Patrick Byrne has never been far from controversy.

He posted elaborate theories on his personal website, railed against an unnamed Wall Street figure he named the Sith Lord and then, last week, delivered the most eyebrow-lifting tale of all. Mr. Byrne — operating on the advice, he said, of the Berkshire Hathaway chief executive Warren Buffett — disclosed that he had been in a romantic relationship with Maria Butina, a woman accused of being a Russian spy who tried to infiltrate circles of political power before the 2016 presidential election.

His statement, with its references to the "Deep State," "Men in Black" and "political espionage," sent his company's shares sharply down and baffled investors. On Thursday, he resigned as Overstock's chief executive and chairman, saying his continued presence was complicating the company's business relationships.

Those relationships, he said in an interview, included the kind necessary to fulfill his plan to sell the online retailer.

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"My presence could — and likely would — be disruptive to strategic conversations that are occurring, one of which is with my most preferred suitor in the entire industry," he told The New York Times. He declined to name that potential buyer.

He also said his presence could lead to problems for the company as it tried to renew indemnification insurance for its directors and officers. "The fact that I am so controversial has never been appealing to them, but I know it is salt in the wound now," he said.