Complex sentence: Political Catholicism had been a major player in interwar German democracy and through the rise of Adolf Hitler, Catholic leaders had often been vocal critics of the Nazis, and Nazi ideologists like Rosenberg had expressed antipathy to Catholicism.
Split into simpler sentences: Political Catholicism had been a major player in interwar German democracy. Through the rise of Adolf Hitler, Catholic leaders had often been vocal critics of the Nazis, and Nazi ideologists like Rosenberg had expressed antipathy to Catholicism.