Why did Darius I divide his state into 20 districts, and put governors at their head?

In order to make it easier for him to manage such a great power, he divided it into 20 districts, put his governors at the head of them.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.