Why Did Trump Lie about the Reason for the Soviet Invasion of Afghanistan?

The Soviet invasion of Afghanistan ended in defeat

In long, rambling session with reporters before his cabinet meeting yesterday, Donald Trump made a bizarre ahistorical assertion that attempted to whitewash the reason the Soviet Union invaded Afghanistan in December 1979.

“The reason Russia was in Afghanistan was because terrorists were going into Russia,” Trump said. “They were right to be there. The problem is, it was a tough fight.”

That may be the Kremlin’s view of what happened, but it runs counter to the assessment of the U.S. government under both Republican and Democratic administrations dating back to the invasion.

So why is Trump, the putative president of the United States, toeing the Russian government’s line here?