So what exactly did Robert Mueller’s weird 10-minute farewell salvo on Wednesday accomplish?

Nothing.

Oh, it fired up the Trump-haters who are ever more loudly demanding impeachment, saying surely Trump committed a crime even though after almost two years and about $40 million Mueller couldn’t quite link him to one.

And it fired up the Trump supporters who say Mueller proved what they’ve been saying all along: The investigation was politically motivated.

Mueller said his 400-page report “speaks for itself” but implied that a DOJ policy that says a sitting president can’t be indicted somehow hampered his findings on the question of obstruction of justice.

But Attorney General William Barr - respected by everyone before he joined the Trump administration and now detested by the left, adored by the right - told Congress under oath that Mueller told him the DOJ policy did not influence his decision to leave the obstruction issue to the Justice Department. Barr said Mueller told him that more than once. With witnesses present.

“When we met with him (Mueller), Deputy Attorney General Rosenstein and I met with him, along with Ed O’Callaghan, who is the principal associate deputy, on March 5th, we specifically asked him about the OLC opinion and whether or not he was taking a position that he would have found a crime but for the existence of the OLC opinion. And he made it very clear several times that that was not his position. He was not saying that but for the OLC opinion, he would have found a crime. He made it clear that he had not made the determination that there was a crime.”

It is not the role of a prosecutor to conclude an investigation, admit that there was no evidence of a crime, then publicly besmirch an individual by saying that the person is not in the clear.

Yet it’s happened before.

That’s what then-FBI Director James Comey did to Hillary Clinton in the summer of 2016.

Democrats were howling then. Republicans are howling now.

I tend to agree with Thursday’s Wall Street Journal editorial, “Robert Mueller’s Parting Shot: The Special Counsel Gave House Democrats An Impeachment Nod,” that noted, “in his public statement Wednesday we saw a special counsel who went out of his way not to absolve Donald Trump and may have put his thumb on the scale toward impeachment.”

The editorial also questioned Mueller’s assertion that he had enlisted a top-notch team of investigators:

“Mr. Mueller finished his statement with an ode to “the attorneys, the FBI agents, and analysts, the professional staff who helped us conduct this investigation in a fair and independent manner.” These individuals, he said, “were of the highest integrity.”

Does that include Andrew McCabe, the former deputy FBI director who is being investigated for lying to investigators? 

Does he mean Peter Strzok and Lisa Page, the FBI paramours whose antipathy for Donald Trump is obvious from their text messages? Mr. Strzok was part of Mr. Mueller’s investigating team until those texts were discovered.

Does Mr. Mueller also mean the FBI officials who used the politically motivated, and since discredited, Steele dossier to persuade a Foreign Intelligence Surveillance Court to issue a warrant to spy on Trump adviser Carter Page? Mr. Mueller didn’t appear to want to investigate that part of the Russia story. Was that behavior of “the highest integrity”?

Mr. Mueller would have better served the country and his own reputation if he had simply done what he claimed he wants to do and let his report speak for itself.

 Instead he has weighed in for the Democrats who want to impeach the President, though he doesn’t have to be politically accountable as he skips town. This is the core problem with special counsels who think they answer only to themselves.”

My theory is that Trump’s relentless criticism of Mueller finally got to the special counsel. Unable to connect Trump to any crimes, he simply launched a hand grenade in the president’s direction and then ran for cover, saying he wouldn’t answer any more questions about the investigation.

But Mueller’s inscrutable actions this week give rise to new questions. Including one about the special counsel’s impartiality.