PewDiePie posting on PeerTube will result with many of his videos being viewed on PeerTube. But either:

• he would make an instance only for himself and majority of his viewers would fail to make a Fediverse account to follow him, or
• he would open that instance for his viewers to make a account there, but then he would be liable for every comment made by his viewers, or
• he would make an account on already existing instance, making a great burden of moderating his viewers for existing administration and moderation team.

An entire network cannot be effectively marketed and accomodate a new users' wave as well as any centralised website, like YouTube, or Bluesky.