Trumps actions spoke much louder than any of his words. He made it a point to never wear a mask every chance he had. trump may have finally believed the virus wasn't a hoax ultimately, probably when he supposedly got sick from it- which I'm believing was a hoax, but to this day, he showed his followers the virus was just a flu by never wearing a mask as little as he did. That tells people he doesn't take the virus personally seriously.
So the trumpettes felt they didn't need to either. He set a tremendous amount of unspoken destructive examples.