It think we have cycles because people remember things that happen in their lifetime but fail to adequately instil that knowledge in the next and subsequent generations. The wealth inequality of the 1920s was the catylist for much of the economic turmoil of the great depression and laid some of the context for the New Deal era. The strong rules for antitrust and managing monopolies were put in place to prevent a repeat and while the generations who lived through the great depression were dominant they survived. As those older generations died out and as the following generations grew in influence those protections were weakened and eventually mostly dismantled, resulting in massive changes from the 70s onwards. Those protections were eroded and wealth and income inequality grew until we reached and surpassed the levels of the 1920s.
I think the same happens for other things like the idea that Nazis are bad or must be resisted, or that religious ideologies should ve kept seperate from the government, or healthcare is something we can help each other to gain, or that workers can have power by working together. What I find hopeful is hearing discussion of all of these ideas in fairly accessible places and people do seem to be studying history in order to avoid repeating it.