What state managers have you used? Why is a state manager needed, and what problem does it solve?

I have used state managers such as Redux, MobX, and Context API in React. A state manager is needed for centralized management of the application's state, especially when data needs to be accessible across different components or modules. It solves the problem of synchronizing state between components, simplifies debugging and scaling of the application, and also helps avoid excessive prop drilling (passing data through multiple component levels). For example, in Redux, the state is stored in a single global store, and components subscribe to the necessary parts of the state, making data management more predictable and transparent.