They also film during the week, which inherently has fewer people. As said before, you can film at different angles and through the magic of editing make it look like a remote location.
They also aren’t part of the herd. Most people will set up where everyone else is, because that must be where the fish are. They need to make a show catching better than just dink panfish, which if you look at popular lakes is where a lot of the people congregate. They move and move and move until they find better fish. They say as much during the show. They are probably one of, if not the most honest fishing shows on tv. They’ll tell you if they didn’t get fish for hours and moved around a ton.