I am by no means an expert, but when I look at the matplotlib library that’s installed on the machine I’m using at the moment (a MacBook Pro 2020), the matplotlib installation does have an __init()__ file (quite an extensive one, actually). For reference, I’m using Python 3.10.2 and matplotlib 3.5.1.
With respect to pyplot, it is a separate library (not a class or method from a file called matplotlib.py) and that affects how you import it in order to use its features. In fact, there is no python file called matplotlib.py so when you import matplotlib you are importing the entire package. It may be helpful to take a look at how to work with python modules, which does a much better job of explaining it than I could ever do.
