Im sure he isn't using any blackhat. I've had videos reach massive amounts of views out of fucking nowhere. I once had a video go super viral and I have no idea how. Most likely he struck algorithm luck, then people stick to his channel because they like his voice or whatever. Also it seems some channels become authorities in certain sub niches, like this cursed minecraft thing, the algorithm may rank him at the top for that so all he does is repeat the same trick a million times until its dry.
I havent tried blackhat but im sure its mostly useless and you just risk getting banned or shadow banned (p-score lowered) so why risk it.
Also, it seems some channels just get stuck in a limbo. Get some viral videos, then the traffic goes away, and it isn't maintained. Further videos don't get recommended. That explains those channels with big amounts of subs but with videos that get few videos. All the videos came from some viral video, but the rest of the videos didn't go viral. It's fucking annoying. Few people become permanently trendy. This guy grew a fanbase and manages to get decent numbers consistently.
I've seen a channel exploiting the same thing right now and he doesn't even use his voice, and this channel is making 1+ million views per video, and they are short 3 minute videos. I don't fucking get it.