On February 7, Donald Trump told Bob Woodward that coronavirus is transmitted by air. “It goes through air, Bob. That's always tougher than the touch. You know, the touch, you don't have to touch things. Right? But the air, you just breathe the air and that's how it's passed," he said. "And so, that's a very tricky one. That's a very delicate one.”
On February 10, knowing that but not telling the public, Trump held an indoor rally in New Hampshire.
On February 19, it was an indoor rally in Arizona.
February 20, Colorado.
February 21, Nevada.
February 28, South Carolina.
March 2, North Carolina.
That’s six indoor rallies held when Trump knew that COVID-19 could be spread by breathing shared air.
And, of course, there was the June 20 indoor rally in Tulsa, which would have been a triumphant return to indoor rallies if people had showed up. But even many Trump supporters knew by that point that being in a crowded indoor space was dangerous. Note that it was the embarrassing attendance, not safety concerns or the death of Herman Cain, that prompted Trump to shift to outdoor events since then.
Trump knew. He didn’t care—putting his ego rush of standing in front of an adoring crowd over the safety of his supporters and public health in the communities they go home to.