I remember reading an interview where Asimov is asked why the books of the Foundation trilogy are so different.
The short answer is that the first book was inspired by an idea he had while talking to a professor about the rise and fall of civilizations.
The others were inspired by pressure by publishers to repeat success, and so he tried to improve and continue the story. This lead him to try and carry the story with characters, which was ironically not why people liked the first book.
The Mule was alright though, even if a little forced.
The short answer is that the first book was inspired by an idea he had while talking to a professor about the rise and fall of civilizations.
The others were inspired by pressure by publishers to repeat success, and so he tried to improve and continue the story. This lead him to try and carry the story with characters, which was ironically not why people liked the first book.
The Mule was alright though, even if a little forced.