Why would you think that? You can just look at the views and get a good sense of what kind of strong following it has on YouTube. For example, if you look at Dungeon craft just as an example, popular videos have 300-500 views, and their Shadowdark video has 100K views: good, but not in a range that would make one logically think that SD competes with D&D.
Active conversations about a game are very much a component of its success, IMO. The fact that lots of youtubers talk about SD is very much an indicator that it has been a successful game.