I certainly learned vi from vi (or I guess vim to be specific). The start page says "type :help or press <F1>", which led me to the help pages (and maybe doing vimtutor, can't quite remember), and then I "learned vi(m)" just working at it, poking and prodding at the various corners (and the manual for is excellent). No Google, no stack overflow, no teacher. Later I started looking up other peoples configurations and stuff, as well as some advanced guides, but I was already basically proficient at that point.

On the other hand: I don't see what's so bad about a product for professionals where you might need a teacher to help you learn. Photoshop is not a simple product to use if you've never interacted with it before and most users go through some tutorial or has a teacher or something. It doesn't mean that Photoshop has bad UX. This goes for lots of software made for professional use: try learning Autodesk Maya or Avid without external resources, I dare you.

Did you read about vi before? How do you know all the shortcuts?

There's not much to learn if you're editing the odd file ... if you want to use vim as an effective development tool, there's loads to learn.