Basically this whole system was doomed to fail. When the Bolschewiki rose to power during and after WWII they created a dictatorship that they labeled "communist". This does not change the fact it was a mere central-authority regime with nationalized industry and little to no free will for the individual. Ifg you compare this to the marxist ideals you recognize it just does not fit. Therer was a philosophic subject, Marxism-Leninism that tried to justify the discrepancies between marx' and other's definition of the communist society and the actual reality.
Under oppression people do not work at peak productivity nor creativity. Add to this the inefficiency that occurs when an omnipotent junta gives each member posts they are not qualified for.
It is a bad circle
after WWI the young soviet republic managed to increase their economic situationdramatically, though in the same time began to establish inefficiency and a terror reign.
If a coal miner was needed the next best worker was given the coal miner job, no matter if he was a better doctor or farmer.
All in all, economic missmanagement combined with much too high expenses for arms and foreign affairs (powermongering) lead to a situation where the soviet economy could not even partly keep up with the west. Gold and foreign (non-communist) currency were harder and harder to get since the east block's products could not compete anymore. (with exceptions though). The bad economic standing (in more than 70 years of "communist" reign there never was really sufficient food supplies) among with the feeling of oppression and an increasing distance between the issues of the common man and the government lead to increasing dissent. If "freedom" or mere wealth was the primary motive for uprisings was the key factor is a matter of ideology but in fact the people lacked both and in the end both are linked to each other. The increasing dissent meat with the reign of Gorbachev who noticed that the hardline stance of the soviet union would lead to a catastrophe. The problem was it was already too late and Gorbachev had no free hand, he had to appease the elites (military, KGB) and the reformers while at the same time keeping the hardships of the reforms as low as possible. Of course it did not work. Gorbachev saw the dissolution of the warsaw pact, more and more nations drifting away to the west. He did not oppose the unification of Germany. He could have done that for some time, but it would not have helped him.
Finally dissent grew within the USSR itself. The Russian federation was governed by Yeltsin who basically was a radical free-market reformer and Russian nationalist. other states mainly in the balticum were not happy at all about soviet regime for they were militarily occupied. Gorbachev tried to create a new union treaty to preserve the union but granbt the nations more independence. Days before he wanted to sign the new union treaty military hardliners couped in 1991. The coup leaders recognized within hours that they would not succeed. Yeltsin got loyal troops around him and ended the coup with relatively few blood. Yeltsin was hero of the day and the union dissolved. Russian nationalism and the unwillingness of the other republics to stay in the USSR made any attempt to keep them loosely together more or less moot. The former soviet states minus the baltics later formed CIS, Commonwealth of independent states, a very loose community of former soviet republics. It soon ceased to be of any importance. Though Russian influence in some former soviet republics continued in the form of military bases. Russia has formally created a "Union of Russia and Belarus", an initiative that keeps Russia and Belarus very tied together. What it actually means is very uncertain. Some say it will eventually lead to a united state, others say it's yet another paper organisation. A united currency was planned but delayed to some point in the distant future. Other states mainly in the south welcome Russian influence as stabilizing factor. The recent actions in Afghanistan and the unsolved conflicts in Dagestan and other 'stans (and the wars in bordering chechnya) may reinforce such welcoming. Only the future will tell if russia gets back any real influence in these states though.
