Why did Weimar Germany produce both Marxist and National Socialist radical extremists?

 (My answer on Quora)

The collapse of the old order, the aftershock of a war lost and the natural economic instability that defines a society in transition are breeding grounds for radicalisms. Their appeal is in offering simple fixes to seemingly insurmountable problems while speaking directly to the masses trapped in a chaotic milieu.

This is all heightened when the center collapses or proves weak and unimaginative in governing.

Weimar Germany was the perfect national incubator for this deadly cocktail just as Revolutionary France was in the turmoil following the demise of the Ancien Regime.

Russia c. 1917–1920 witnessed this phenomena as well as the various mutations on the Far Left and the Right wrestled for power. The Bolsheviks of course would ultimately prevail.