They had two desires that conflicted on one hand they wanted their military to take over the world, on the other they wanted to stay in power themselves. Most of the world the military is the "reset" button. When things go very bad the military steps in and puts things back on track. Sure you may have a guy in a funny uniform running things but they are generally not interested in starving you to death to try to advance some cockamamie theory about the New Soviet Man.
So they built up their military in public but in private they made sure the State Security kept a close eye on the military especially the upper level officers.
You may be the General but your political officer could over rule your orders and may just shoot you out of hand.
Since they had conscription they did not need to attract people to join the military, they did so at gun point, stayed in at gun point and sold everything out of the back of their trucks just to stay fed and clothed.
The closest the Russian military was to being fully supplied was when the US was doing it during WWII. In retrospect that probably was a mistake.
There is little question that the Russian military has inherent shortcomings. As you say political interference and overt corruption has caused it to be often inefficient, technologically challenged and as a result take inordinate causalities. Yet many Americans who live today would have never come to exist if it were not for the courage, endurance and solid fighting done by the Russians. The Russians despite all those handicaps decimated the best elements of the German army. Try to imagine if the American army had to attack and liberate Europe with the German army largely intact. Many of the fathers and grandfathers who did come home and ignited the baby boom would have died and never procreated. Americans owe a great debt to those Russians who sacrificed and fought so well despite everything.
To put that another way: Authoritarian countries can not have efficient military forces. It would be fatal to the regime.