Maybe because they were commies and this whole captialism thing was new to them? Exactly who was going to pay for the upgrades and how?
There were businessmen who created a successful business out of the factories and then there were thieves who cheated the stock from the workers for practically no price and then scrapped the whole functional plant for a quick buck.
I heard stories that high quality milling machines were sold for scrap metal when you could have sold them on the regular market for $10000. This means that the persons behind the selling did not:
A) Give a rats bellybutton about the workers OR the economy of the whole nation
B) Were greedy as hell and opted to have 10% immediately instead of getting 100% in the long run.
These people did a serious crime against thier nation as they crippled a large chunk of the production capability which was a requirement for any kind of capitalist system to work in the first place. The workers aided in this because they had no idea at that time of the value of the stock. Even if they did, they were extorted and threatened to sell (mafia works well in Russia.)
Well, some of those machines were sold later for 10x the price as soon as they passed over the border. Still a bargain for any western machine shop.
One of the things SU was good at was milling machines and optics (surprising, coming from me isn't it?
). You could buy high quality optics for a camera for a fraction of the western price.