Complex sentence: The Nazis stopped goose-stepping (known to them as the Stechschritt) in the 1930s: they only used it during the Nuremberg rallies, and it fell out of fashion; no new recruits were asked to do it.
Split into simpler sentences: The Nazis stopped goose-stepping (known to them as the Stechschritt) in the 1930s, they only used it mainly during the Nuremberg rallies. It just fell out of fashion and no new recruits were asked to do it.