The reasons President Trump picked Michael Flynn for national security adviser were pretty well known: The retired lieutenant general had experience in the murky world of U.S. intelligence, and, perhaps more important, was a fiercely loyal voice on the campaign trail — a supporter who hopped on board before it was popular.

That early loyalty got Flynn a prime speaking spot at the Republican National Convention in July. And looking back on that speech now, Flynn had pretty strong thoughts about a certain government official mishandling intelligence.

Retired Lt. Gen. Michael T. Flynn called for Hillary Clinton to drop out of the presidential race on July 20, 2016 at the Republican National Convention in Cleveland. (Republican National Convention)

“Lock her up, that's right!” he chanted along with the crowd at one point in his speech. “Damn right, exactly right. … And you know why we're saying that? We're saying that because, if I, a guy who knows this business, if I did a tenth of what [Democratic nominee Hillary Clinton] did, I would be in jail today.”

Let's be clear here: Flynn has not been accused of any crimes, although it has been suggested he may have been in contravention of the Logan Act, a law dating to the 1700s. (That law has never been used to prosecute anyone.)

Fast forward seven months from the GOP convention, and Flynn has stepped down as national security adviser just 24 days into the new administration — a shorter tenure than anyone who has ever held the post before. The biggest reason for his resignation is that he mishandled a delicate situation with a foreign power — Russia, no less, the country with which he had already been accused of having too-close ties — and then failed to disclose the whole truth to the incoming vice president when asked about it directly.

Flynn, as he said at the Republican Convention in July, is “a guy who knows this business.” And as such, he probably realized sometime recently that failing to disclose the whole truth to one of his bosses, and the appearance of improper contact with a foreign enemy, would be enough to sink his job.

He was right then — and now.