But he's not even outside their circles right? Doesn't 3b1b have a PhD? I can tell you at least that we watched some 3b1b videos in my university undergrad math classes last year!
That's so encouraging to hear, I would've loved uni maths with some high quality videos like his to watch, even if just for after class to reinforce the topics.
Wikipedia thinks he has a Bachelors from Stanford[1]. That said, I love his videos too. I started with The Essence of Linear Algebra[2], which is just fantastic and really shaped my intuition for the topic.