A million followers is one in 350 Americans.
I suspect he isn't even preaching to the whole choir.
A million followers on YT is a heck of an achievement for a single topic, considering most YT channels I’ve seen struggle to get 10-50K. And don’t forget the news shows, which probably reach a lot of people who don’t do YT. Yep, Mr. Noir is one of the better-known 2A commentators, I’d say.