Honestly it's not even that much. Pro players will feel it but pubs will likely be completely fine with this. Fights in pubs are messy and drawn out enough that the procs will still come.
I'm not really addressing that facet of the topic, I was addressing whether those subs would be enough to keep his career afloat. But for the record, I'm not going to be subscribing as I also do not appreciate his behavior.
That could be short term. Oftentimes I hear about these people getting more followers, but then I don't hear about them ever again. There are exceptions to that obviously, but I'm not entirely certain on how many retain that fame.
Subscribers is a big number for YouTubers, but if I'm not mistaken, views for videos is still more important. And I wonder how easy it will be to continue making this kind of content a) after suffering an injury like this which will put him out of commission for a while and likely prevent him from doing particular stunts, and b) with the general hesitancy to approach people that this altercation will hopefully instill. So he could be looking at paying actors (would go poorly) or making his pranks more tame (would go poorly).
Niche comes with volume too. And really, niche is what's important, not the broad strokes (I'd argue the boons of Lemmy are broad strokes at least). Reddit is worse for a lot of reasons, but man oh man, how can you convince someone to come over when the value is in the volume? I'm still primarily on Reddit, actively contributing to the problem.