How did piediepie became the Lord of altright so quickly?
They realised one of the most popular people on youtube potentially had sympathies for their worldview - or at the very least was an ignorant enough dudebro not to critically analyse it - and thus positioned themselves as his most loyal, hardcore fanbase, encouraging him to lean into them harder, particularly through cross-promotion with youtubers much more openly of that tilt. The fact that he's a Swede probably helped, because the alt/far right still have a hard-on for Scandinavia.
All reinforced by the fact that the default MO for youtubers is to position themselves as 'just a guy'. They're not
really telling you what to think. They can't
really make people do stuff. Assertions like that of the teacher run counter to this supposed concept - this very foundation of the grassroot marketing of Youtubers - because it suggests that not only does someone like PDP have actual power and influence, but that he is wielding it to a negative end. That I think is what earns PDP's ire most; the suggestion that he is not merely 'just a guy', but in fact, a bad guy. Which he can't be. He's just a guy.