It's also a factor of Russia not competently executing the initial invasion and got themselves bogged down. Similar to the Germans in WW1 on the western front, they got bogged down before they could take their key objectives, but the eastern front remained mostly mobile during the war because of the vast size of the front, and they eventually won on that front. Because you either win by our maneuvering your enemy an encircling them, or attriting the hell out of them till they have nothing left, and I think the pendulum has swung again towards a defensive advantage, especially with UAVs and remote mine laying systems, and precision artillery munitions.

It's a big part of why US doctrine is so focused on quick fast and overwhelming assaults and a strike first mentality. Even in Desert Storm they were severely worried about being bogged down by the Iraqi Army and starting a prolonged conflict with massive American losses. So it was imperative to flank the Iraqi Army from the western desert by the French Armored Corps.