My experience has usually been that Wikipedia is an abysmally bad tool for learning mathematics. The articles seem to be written by someone who has zero clue how to teach the concepts and merely is trying to wow the reader with their proof-writing skills.
That is because the majority of Wikipedia's math articles are actually from Planet Math, a website full of math knowledge similar to MathWorld that is geared towards mathematicians.
That's because Wikipedia isn't a tool to learn mathematics. Wikipedia articles (on anything) are not meant to teach about a subject (in the sense of schooling) but rather to give an exposition of a subject. It is considered to be very bad style on Wikipedia to write articles that try to teach the reader as a textbook or a class would.
