Comparing Russia's military options in 2014 and 2021, it seems that cost-benefit analysis of a large-scale military operation looked much more favorable in 2014. After all, Yanukovich was the recognized head of state, and he could have requested Russian troops to protect the country from the civil war. In this case Russia would have achieved the effective control of Ukraine at a miniscule fraction of the cost they'd have to pay today, since they would:
- not be fighting an organized army;
- face few if any international sanctions;
- encounter little or no guerilla resistance afterwards;
- face a much smaller risk of domestic pushback due to casualties;
- contribute much less towards the unity of the NATO and the West.
If Yanukovich could not be persuaded to ask for the troops, Russia's costs would skyrocket, but they would still be much smaller than today because:
- Ukraine's military was almost completely dysfunctional;
- Ukraine was not on the Western political radar;
- entering a country without a government and in the middle of an internal conflict causes much less resistance from the population.
What factors could have contributed to Russia's decision to not use its military to either preserve the Yanukovich government, or to install a new pro-Russian government in Kiev?