Are angular material and material-ui and Materializecss related to material design?
If you learn one does it make it easy to learn and apply the rest?
Yes, they are all related to the Material Design design language, which may help knowing what components you need for a given website, however; they all use very different technologies and programmer interfaces.
For instance, learning Material UI for React with its properties, events, styling method, etc. don't translate well into MaterializeCSS with it's completely different developer interface, but you may know that for a given project, you will need card components even if how you create them is different.
I'd you're looking for where to start to get into a Material styled framework, pick the one relating to the framework that closest matches your needs or your existing experiences.