The timeline starts diverging when Wolfgang Kapp decides to hold a rousing speech at the Reichstag instead of trying the coup the Weimar Germany. Without this inherent weakness, the Weimar Republic struggles on. Eventually, Paul von Lettow-Vorbeck takes power in Germany while Hitler starts a civil war in Austria (which is promptly annexed and pacified by Germany). Without a powerful belligerent country in Central Europa, Stalin's Soviet Union focusses on Asia, taking on Japan. The original thread can be read here. The condensed version is here.