I seriously think half the criticism of the show is from people who don’t know this kind of important world detail because they only read the main Foundation trilogy where Demerzel, Raych etc don’t even appear.
Most people don’t realize Foundation is not 3 books but like 14
Caves of Steel
Naked Sun
Robots of Dawn
Robots and Empire
Pebble in the Sky
Stars, Like Dust
Currents of Space
Prelude
Forward
Foundation
Foundation and Empire
Second Foundation
Foundations Edge
Foundation and Earth