One thing I never understood about the Soviet Union were the famines and near-famines; those that were not explicitly engineered by the regime like Holodomor.
How could a nuclear power suffer from famines and near-famines?
These problems with food production even continue to this day; as Russia has been a huge importer of food from the European Union until recently. One would think that a producer of technological wonders, both during the Soviet-era and since, would find a definitive solution to these food production problems.
Why was or has no definitive solution been found and implemented, seemingly to this day?
Agronomy hardly seems to be rocket science, and also there was and still is a lot of fertile land available.
EDIT: Chief among the famines would be the famine of '47, when the Soviet Union was firmly walking on the nuclear path (the first nuclear test was made in '49). Incidentally, this was also the year when a "technological wonder", the AK-47, started being produced. We can still read about this weapon in daily news. Among the near-famines I thought about the post-WW2 bad harvests and systemic failures in agronomy, that made grain imports necessary. These might have developed into true famines.