A few of the more egregious examples: Throughout 2016, the report found , Paul Manafort, President Trump’s campaign chairman, gave private polling information to Russian agents and shared campaign strategy with them; in June 2016, Donald Trump Jr., the president’s son, arranged a meeting with Russians at Trump Tower in the expectation of getting “dirt” on the Hillary Clinton campaign; on July 27 of that year, candidate Trump publicly called on the Russians to hack Mrs. Clinton’s emails, five hours before they attempted to do just that; the campaign then devised its strategy and created its messages around WikiLeaks’s releases of stolen files from the Democratic National Committee.

Nearly all Republicans on both committees failed even to acknowledge the threat posed by Russia and other countries. With significant exceptions like Will Hurd, representative of Texas, Republican lawmakers seemed much more focused on protecting Mr. Trump and deflecting any concerns about electoral security by impugning Mr. Mueller’s integrity, attacking the origins of an investigation that he did not initiate, and — in one particularly disgraceful jab by Guy Reschenthaler of Pennsylvania — accusing his investigative process of being “un-American.”

In another era — the time Mr. Mueller seemed to hail from — an attack by a foreign government to divide Americans and upend their elections might have produced a different response. It might have drawn legislators together to develop a bipartisan initiative to make clear, as Adam Schiff, the chairman of the House Intelligence Committee, put it, “that we, the people — not some foreign power that wishes us ill — we decide who shall govern us.”

Yet for all the bluster and misdirection — about Fusion GPS, the Steele dossier, the texts of Peter Strzok and Lisa Page — the Republicans offered little pushback against Mr. Mueller’s key revelations.

Of course Mr. Trump and his senior campaign staffers and associates didn’t worry that what they were doing was wrong. The 2016 campaign was providing too many opportunities to pad their bank accounts. From Mr. Manafort’s efforts to leverage his position to extract himself from a multimillion-dollar debt to Mr. Trump’s own attempts to build a giant hotel in Moscow, self-dealing permeated the Trump campaign. Remember, as late as weeks before the election, Mr. Trump and most of his top advisers thought he had no chance of winning. The real purpose of the campaign was to build up the Trump brand, and be the “greatest infomercial in political history,” as Michael Cohen, Mr. Trump’s personal lawyer, phrased it.