From what I heard, youtube has cut revenue to content creators across the board in recent months or years, and that goes for a lot of subjects beyond guns.
Yup. Used to be you could make decent bank just off YouTube ad revenue, if you were popular enough. Not so much any more.
I'm not really sure advertising was ever all that great a way to make revenue, in the long run. Advertisers, and the audiences they are trying to reach, are too fickle. Hence the turn to direct funding from viewers.