Okay I try and as usual my tries are shaky.
Germany wins ww1 and creates a Mitteleuropa puppet system in Eastern Europe. The prewar Wilhelmine society stays: Authorian and the Prussian elites stay at the helm, while the SPD is curtailed. In Russia the Reds dont win, but a shaky white dictatorship prevails. After some years a extremist, revanchist wing comes to power and starts ww2 by invading Eastern Europe to recreate the Russian Empire in its 1914 form. The White Army conducts numerous massacers on their way to Berlin.
Like in OTL the first phase works, but in the end, the German Reichswehr goes on a counter attack against the Russian steamroller and wins. Post war we see the Mitteleuropa system stays and look much like the Warsaw pact. And, who would have thought it? In 90 the system breaks down and leaves many Germans in Eastern European States, like some of the Baltic Nations, parts of Poland and CS.
After twenty years of Self finding the German Empire is back and wants to protect the Germans living in other states. While these states choose Russia for protection.
Voila, a "little" bit of handwaving, but tell me what you think.