As soon as I turned on a television here I wondered if I had arrived through an alt-right wormhole.

Back in the States, the prevailing notion in the news was that Mr. Assad had indeed been responsible for the chemical strike. There was some “reportage” from sources like the conspiracy theorist and radio host Alex Jones — best known for suggesting that the Sandy Hook school massacre was staged — that the chemical attack was a “false flag” operation by terrorist rebel groups to goad the United States into attacking Mr. Assad. But that was a view from the fringe.

Here in Russia, it was the dominant theme throughout the overwhelmingly state-controlled mainstream media.

On the popular Russian television program “Vesti Nedeli,” the host, Dmitry Kiselyov, questioned how Syria could have been responsible for the attack. After all, he said, the Assad government had destroyed all of its chemical weapons. It was the terrorists who possessed them, said Mr. Kiselyov, who also heads Russia’s main state-run international media arm.

One of Mr. Kiselyov’s correspondents on the scene mocked “Western propagandists” for believing the Trump line, saying munitions at the air base had “as much to do with chemical weapons as the test tube in the hands of Colin Powell had to do with weapons of mass destruction in Iraq.”

That teed up Mr. Putin to suggest in nationally televised comments a couple of days later that perhaps the attack was an intentional “provocation” by the rebels to goad the United States into attacking Mr. Assad. RT, the Russian-financed English-language news service, initially translated Mr. Putin as calling it a “false flag.” The full Alex Jones was complete.