A couple of books I'd recommend if you're interested in understanding it are 1) The Nazi Doctors, by Robert J. Lifton, and 2) The Road to Serfdom, by F. A. Hayek.
Neither book alone will do it, but the two combined ought to put you well on your way to understanding the psychology of how things can reach the point they did in Nazi Germany.
This book is well researched, sourced from the diaries of FDR's first appointed ambassador to Germany, William Dodd, and from his family's papers. He and family were in Berlin from 1933 to 1937, and saw the day to day ratcheting up of violence and political power. The book covers the internal politics of the National Socialists, the attitudes held in the US State Dept (not surprisingly anti-Semitic, "ruling class" Harvard/Yale types, snobs), and about people they came to know in Germany who simply disappeared, some to the camps that were running even then. This is all well before the official decision in 1942 to mechanize murder on a mass scale (which is another whole area- the Wannsee Conference).
Once you get into this book, the reality will hit you (they were there in real-time) of how this movement developed into institutionalized hatred and murder (not just of Jews, but Catholics, Protestants (Lutherans), gypsies, Poles, masonics- even communists who helped them come up-anyone who was in the way of a totalitarian elitist socialist state). It describes how it was a Leftist movement that started with a wide leftist spectrum. Eerie parallels to the views and actions of the socialist/marxists who are trying to takeover the US today.