Well, he did read Edward Gibbons "Decline and Fall" before he pitched his idea for Foundation, if I remember correctly. The "foundation" of Foundation is therefore not rooted in fictional prose but in history, both in writing and philosophy. The changing characters are vehicles for exploring various forces that propel history like technology, trade and religion. The first book especially is a step by step description of how europe got through the very early medieval period after the fall of the western roman empire.

The narrative is more stringent and less episodic in the other two but the various philosophies of Historiography stay at the core of Foundation, for the most part. That's where the trilogy draws it's strength from and got it's accolades