They took inspiration from the prussians before them.
And those became ww1 uniforms which inspired the ww2 outfits, because it was clean cut and looked good on parade. It inspired uniformity and their own history that the allies "tarnished" by winning and ruining their economy (that gave rise to hitler)
This made me think of a scenario: a countrymapper kid grows up and becomes a vlogger. Should Porsche have made tanks, they’d flex with a Porsche tank instead of a Porsche car.