I recently wrote a post called "The History and Implementation of React-Redux" [0]. It covers the basic process of how Redux works with a UI, the benefits of using React-Redux, and the specific implementation details of how it optimizes React rendering updates for you.
[0] https://blog.isquaredsoftware.com/2018/11/react-redux-histor...
I can see why the Flux concept would seem arbitrary and overengineered if you hadn't been forced to solve that particular problem before. For me, the baffling parts of Redux were the ones that were specific to React, because my understanding of React was very shallow. The amount of React I had to learn to understand React/Redux felt like way more than I would have needed to learn to write an app without Redux. But for me, it was worth the effort to be able to use Redux for state management.