What is the "contradiction" of the 1920s?

But the 1920s were an age of extreme contradiction. The unmatched prosperity and cultural advancement was accompanied by intense social unrest and reaction. The same decade that bore witness to urbanism and modernism also introduced the Ku Klux Klan, Prohibition, nativism, and religious fundamentalism.

in 550 b.c.e. cyrus the great, the leader of the persians, conquered the medes and united the iranian people under one ruler for the first time. cyrus became the first king of the persian empire and went on to establish one of the largest empires in world.

i think it was because of how protected egyptian civilization was was which allowed them to evolve without much outside influence.