[Tainnor]

It's not about being in the top of the field. Even just getting to the point of being able to halfway competently talk about mathematics takes a grueling amount of work.

> Plenty of independent learning / pop textbooks are written by "normal people" who aren't tenured professors.

Idk, Simon Singh is one very well known example of "pop maths" and he has a PhD in particle physics, that's quite a bit more than just "do the reading for a year". Other examples like Eugenia Cheng and Ian Stewart are similarly credentialed.

It's the same in other fields, really. Yes, you can learn to play simple tunes on the piano relatively quickly, but even just being able to play the full Für Elise just takes so much more than that. Or you can learn Hiragana relatively quickly which I guess means that you understand more about Japanese than 95% of people, but it'll still not be enough for you to engage with Japanese in any meaningful way.

The beginner stage is always the easiest. It's after that that it gets really hard.