Why is Donald Trump so eager to protect Mike Flynn?

In Thursday's hearing, fired FBI Director James Comey made clear that President Donald Trump did not ask him to close the broad Russia inquiry. Rather, when Trump asked Comey to "let this go," Trump was referring specifically to the ancillary criminal investigation into whether former national security adviser Mike Flynn lied to FBI investigators.

So Sen. Angus King asked Comey whether closing this narrow aspect of inquiry would have interfered with the broader Russia investigation.

"No," Comey said. Then he paused to think, and said it was "unlikely." And then he proceeded to describe how halting the criminal inquiry into Flynn could possibly interfere with the broader counter-intelligence inquiry.

"There is always a possibility if you have a criminal case against someone, and you bring it and squeeze them, you flip them and they give you information about something else," Comey said.

Trump talks a lot about "loyalty," but loyalty for him is usually a one-way street: Others are supposed to be loyal to him. Comey even said Trump told him it would be a good thing if the Russia investigation flushed out untoward activity by other campaign satellites of his.

But when it came to Flynn, Trump leaned on Comey to back off. With Flynn, Trump's loyalty is a two-way street. Why? Is it that he has special personal affection for Flynn? Or is it because he is afraid of what Flynn might tell prosecutors to get out from under a criminal investigation?

I am not positing that Trump and Flynn engaged in a treasonous, quid-pro-quo scheme with the Russians. That seems too complicated, and there are simpler explanations for Trump's pro-Russia behavior and Russia's pro-Trump behavior.

But I am positing that Trump is a person with no ethical standards who openly describes himself as "greedy," and that Flynn is a person who has shown a willingness to take personal payments from hostile and quasi-hostile foreign powers and then act in his official capacities to benefit those foreign powers. And I am positing that Trump and Flynn had a tendency to get up to no good together.

Who knows what unknown unknowns are out there - and what Trump and his buddy Flynn could have gotten up to.

"In any complex investigation, when you start turning over rocks, sometimes you find things that are unrelated to the primary investigation that are criminal in nature," Comey said Thursday.

There are certain rocks that Trump seems to have really not wanted turned over - rocks he told the FBI director he "hoped" he would not turn over, and rocks he seems to have fired the FBI director out of his frustration that they might be turned over.

I would like to know what's under those rocks.