According to a grand-jury indictment released last week, Russians conducting an illegal social-media campaign in the 2016 elections were instructed to support not just Donald Trump but Bernie Sanders as well.

Sanders, for one, is none too happy about it.

As he explained it on “Meet The Press,” Sunday, Russian interference constituted an attack on our sovereignty and form of government, and it was time for America to send Moscow a message before the 2018 midterms: “You are doing something to undermine American democracy; you are not going to get away with it. This is a major assault. If you do that, there will be severe, severe consequences.”

The other 2016 beneficiary of Russian meddling took a very different course over the weekend. In more than a dozen Russia-related tweets, Trump lashed out at a variety of targets. He blamed President Obama for not halting the operations. He attacked the Democrats, suggesting that they had somehow colluded with the Russians who were attempting to push Trump’s candidacy. He attacked Hillary Clinton and CNN, and also criticized his own national security adviser, who had dared to say that evidence of Russian meddling was now incontrovertible.

Trump even attacked the FBI, suggesting that if it hadn’t devoted so much attention to the Russian meddling investigation, 17 students and teachers in Parkland, Fla., might still be alive:

We all know our president to be a man without moral compass, a man whose sole concern is himself. But hijacking the bone-deep anguish of those poor people in Parkland for his own self-protective purposes? That represents a new low that some will nonetheless find a way to defend.

But here’s the thing:  Somehow, in all those tweets attacking all those people and agencies, Trump never once condemned or criticized the Russians or Vladimir Putin., the people who actually committed the crime in question. He never once expressed the slightest bit of anger or concern at what they had done in 2016, or what they might do in 2018. The man who is perpetually in attack mode, who launches verbal and Twitter attacks at the slightest provocation, has never once trained his guns in the direction of Moscow.

As recently as November, in fact, Trump was still saying that he accepted Putin’s claim of innocence, despite the unanimous opinion of the U.S. intelligence community.

"Every time (Putin) sees me, he says, 'I didn't do that,' " Trump said. "And I believe -- I really believe -- that when he tells me that, he means it.”

It is just bizarre: Trump could easily do what Sanders has done, which is to forthrightly condemn Russian meddling and demand that action be taken both to punish Putin and prevent a recurrence. That would be the obvious course of leadership for a man in Trump’s position, the only course that makes sense politically and for the nation. Yet he refuses to take that obvious course of action.

Why? What explains his silence? You run through the possible explanations, and almost none of them makes sense. So perhaps we should turn to the greatest detective and problem-solver the world has ever known, the brilliant Sherlock Holmes.

It is Holmes who tells us that “As a rule, the more bizarre a thing is the less mysterious it proves to be,” and also that “when you have eliminated the impossible, whatever remains, however improbable, must be the truth.”

In “The Adventures of Silver Blaze,” one of the classic Holmes stories, the detective is trying to figure out who had sneaked into a barn and made off with a famous race horse without being detected.  The answer, Holmes suggests to a policeman from Scotland Yard, might be the “the curious incident of the dog in the nighttime.”

"The dog did nothing in the nighttime," says the policeman.

"That,” says Holmes, “was the curious incident."

The guard dog did not bark because it recognized its master -- its master was the perpetrator of the crime.