WASHINGTON — The report that had much of Washington buzzing on Thursday required 500 pages to outline its findings, but to President Trump, three words mattered most — “we’ll stop it.”

Those were the words that a senior F.B.I. agent texted in August 2016 to a colleague who was worried that Mr. Trump would win the election. For the president, that text seemed to validate his claim of a “deep state” conspiracy out to get him.

But the same inspector general report also undercut Mr. Trump’s narrative. Whatever the agent, Peter Strzok, meant, the F.B.I. did not “stop” Mr. Trump, nor did the inspector general find evidence it tried. To the extent that the F.B.I. and its director at the time, James B. Comey, did anything wrong in 2016, according to the report, it was to the disadvantage of Mr. Trump’s opponent, Hillary Clinton.

The sprawling report, the most comprehensive look back at the investigation into Mrs. Clinton’s use of an unclassified private email server, reflected a messier reality than the simple story line promoted by the White House: An array of senior officials at the F.B.I. and the Justice Department made mistakes, the inspector general determined, but he found nothing to conclude that anyone went easy on Mrs. Clinton or tried to harm Mr. Trump out of political bias.