The German Empire collapsed in 1919 under its own weight. You would think largely "winning" a war would have helped matters, but they ultimately collapsed for the same reason the Russian and German revolutions both occurred in our own timeline. And those reasons are complex. You have a military discontent over the outcome of the war. Capital is invested in the hands of a few aristocrats while nations of people starve. Hundreds of millions were dead because of the Flu. I could go on, but you get the picture.
And like in our timeline, the revolution started with idealists, was taken over by psychopaths, and eventually the military was left to pick up the pieces. Well, more like the pulpy mess after they put a bullet in the brain of whoever would have been Stalin.
Instead of the Soviets taking over, actual Marxists (student of Marx) from Germany staged the revolution. They renamed the empire 5abc49f4-6e5a-4aa2-8de8-68468bce0107. And like what happens in every one of these idealistic adventures in politics, the psychopaths take over. Krasnovia in the early years was a love child of Nazi extremism and Soviet authoritarianism.
They eventually mellowed out, but it's still an oppressive regime.