Democratic presidential nominee Hillary Clinton addresses the crowd on July 28, 2016, the last day of the Democratic National Convention, in Philadelphia. (Ricky Carioti/The Washington Post)

Robby Mook, a CNN political commentator, was Hillary Clinton’s 2016 presidential campaign manager.

New filings by special counsel Robert S. Mueller III on Friday provided fresh clues about where the investigation into Russian interference in the 2016 presidential election is headed. Mueller’s filing said President Trump’s former personal attorney, Michael Cohen, was contacted in 2015 by a “Russian national” seeking “synergy” between Trump’s campaign and the Russian government. The special counsel’s team also said Paul Manafort, Trump’s former campaign chairman, lied about meeting with Konstantin Kilimnik, whom the U.S. government has linked to Russian intelligence.

The Mueller filings made news, of course. But how much has what we know about Trump and Russia really changed since 2016? Not as much as you might think.

On the Friday before the Democratic National Convention in July 2016, Russian agents released, through WikiLeaks, thousands of emails stolen from the DNC. The timing caused maximum harm at a critical moment in the Democratic contest. As campaign manager for Hillary Clinton, I appeared two days later on two Sunday political talk shows, ready for an avalanche of questions about the emails, which I got. But rather than focusing on the content of the documents, I thought it was important to discuss why they were released in the first place.

“Experts are telling us that Russian state actors broke into the DNC, stole these emails, and other experts are now saying that the Russians are releasing these emails for the purpose of actually helping Donald Trump,” I told Jake Tapper on CNN’s “The Lead.” I wasn’t offering my opinion; I was stating what cybersecurity experts had determined.

Weeks before the emails’ release, the Russian connection was already clear: The Post article that on June 14 broke the news of the DNC hack said in its headline that “Russian government hackers” were the culprits. Vice News’s Motherboard reported two days later that some of the technology used to process the stolen documents employed Russian language settings, and one username referred to the first head of Soviet intelligence.

The affinity between Trump and the Russian government by that point was already so apparent that Politico Magazine’s May/June issue had run a lengthy article referring to him as “The Kremlin’s Candidate.” Also in May, Trump had named Paul Manafort as his campaign chairman. Manafort had been a lobbyist and consultant for pro-Vladi­mir Putin Ukrainian President Viktor Yanukovych, before Yanukovych’s ouster in a 2014 coup, and an adviser to Russian oligarch Oleg Deripaska.

At the Republican National Convention in mid-July, the Trump campaign, seemingly out of the blue, had twisted arms to make the GOP platform more Putin-friendly. Unusually, the convention was attended by the Russian ambassador to the United States, Sergey Kislyak. Earlier that month, Trump foreign policy adviser Carter Page had given a speech in Moscow criticizing the United States for its “often hypocritical focus on democratization” and praising the Putin regime.

We knew all of this at the Democratic National Convention. And yet when I and other members of the campaign repeated that Russia was responsible for the hack and was doing this to help Donald Trump, many in the press seemed skeptical, treating the assertion as mere spin. A lot of people appeared to believe that the idea of Russia helping Trump was far-fetched. Even some of our staunchest supporters seemed to think I might have lost my marbles.

Election Day was long gone before Russia’s interference in the campaign — and the possibility of the Kremlin’s coordination with agents of the Trump campaign — was widely accepted. Even today, some people still muse about whether the Trump political operation could have been in contact with culprits of the DNC hack. Yet longtime Trump associate Roger Stone said repeatedly in 2016 that he had been communicating with WikiLeaks founder Julian Assange. Lately, Stone has denied being in touch with Assange, and last week Stone’s lawyer informed the Senate Judiciary Committee that his client would invoke his Fifth Amendment right not to testify in the committee’s Russia investigation.

Obviously, much more evidence about Russia’s interference has come out since 2016. But I’m not sure we’ve learned the bigger lesson: Why did it take two years and dozens of indictments for so many to believe that Russia was not only behind the DNC hack but may also have been in cahoots with the Trump campaign, when there was so much evidence at the time?

It’s as if something needs to be secret or hidden to truly matter. If it’s sealed in a courtroom, it must be a bombshell, but if it’s out in the open, it’s just not as serious.

Trump will not be the last of his kind. The next time so much evidence about a candidate is sitting out in plain view, let’s hope it gets a good look before Americans cast their votes.