This is definitely mostly true, with several reasons applying.
The best rise to the top. You don’t see the bad ones on YouTube.
The can teach in a variety of ways. Some will mesh with your learning method, others won’t (but mesh with other people’s methods).
You only need 1. Schools need 1000s of teachers, and they each only teach a few students. An online YouTuber can teach 1,000,000s, if they are good enough.
No paperwork. 80% of a teacher’s job is paperwork. 15% is playing nanny to a bunch of kids, 5% is actually doing the teaching.