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.

a peace conference held after the surrender of japan

an international conference held near the end of world war ii

a meeting of the victorious nations after the defeat of germany

a summit meeting between the united states and the soviet union