Related: why was the Russian peasantry so left wing relative to the "sack of potatoes" of Marx's description? Was it just a mass failure of the Stolypin reforms?
I am extremely under-qualified to answer this, which bugs the Hell out of me--because why did I waste so much time reading studies of comparative revolution from the 60s?--but my impression of the Stolypin reforms was that their greatest failure was their incomplete execution, owing to his conveniently-timed assassination.
Perhaps relevant--and possibly contradicting the above--Eric Wolf's view was that revolutionary peasants came from the middle section of their class that was far from content but had enough property and autonomy to risk breaking with the nobility and the state. Perhaps the German situation lacked this arrangement for one or more reasons? I am thinking here maybe successful proletarianization of agriculture, or in the opposite direction a peasantry that was utterly dependent on feudal lords. I don't know enough about Germany to say either.