chapotraphouse

The Soviets were very rail dependent and as other have mentioned had wide gauge. The extensive rail transport meant that roads were lower priority. By contrast, the Germans largely Horse-drawn logistics were reliant on roads, especially once they hit Soviet rail networks where their trains were inoperable (the Soviets were pretty good at preventing rail stock capture.) The soviets also used animals but more mules with saddlebags/sleds and not heavy carts.