"Simpson and Fritsch acknowledge that several of Steele’s most sensational allegations remain unproven and that others were almost surely wrong... [but] 'a spy whose sources get it 70 percent right is considered to be one of the best'..."

"and... while reporters focussed on the most salacious details, they 'tended to miss the central message,' about which they say Steele was largely correct. They note that, in his first report, in June, 2016, Steele warned that Russian election meddling was 'endorsed by Putin' and 'supported and directed' by him to 'sow discord and disunity with the United States itself but more especially within the Transatlantic alliance'—six months before the U.S. intelligence community collectively embraced the same conclusion. Steele also was right, they argue, that 'Putin wasn’t merely seeking to create a crisis of confidence in democratic elections. He was actively pulling strings to destroy Hillary Clinton and elect Donald Trump,' an assessment the U.S. intelligence community also came to accept. And they note that, as of September, 2019, U.S. officials confirmed that the C.I.A. had 'a human source inside the Russian government during the campaign, who provided information that dovetailed with Steele’s reporting about Russia’s objective of electing Trump and Putin’s direct involvement in the operation.'"

From "The Inside Story of Christopher Steele’s Trump Dossier/In a new book, the founders of the firm that compiled it defend their work" by Jane Mayer (in The New Yorker).

About those "sensational allegations":

Steele’s first report found that Russia had tried to cultivate Trump by dangling business ventures and had been accumulating blackmail material, including what later came to be known as the pee tape—ostensibly a recording showing prostitutes entertaining Trump by urinating on a hotel bed, at the Moscow Ritz-Carlton, in which the Obamas had previously slept....

Despite the fact that the fabled pee tape has never surfaced and Trump immediately denied its existence, Simpson and Fritsch write that Steele remains confident that his reports are neither a fabrication nor the “hoax” of Trump’s denunciations. Trump’s defenders have claimed that Steele fell prey to Russian disinformation, and so, therefore, it is he, not Trump, who has been a useful idiot for the Russians. But Steele tells the authors, “These people simply have no idea what they’re talking about.”