Russia thought it would take days to seize Ukraine. 4 years later, war is still raging

[haele]

19. The Oligarch Russians mistook the ease of the 2014 taking of territory

With the post-Maidan situation - after the Ukrainian economy and quality of life had improved and both the Ukrainian Parlement and the Military had been purged of a significant number of old Soviet/Russian agents and sympathisers.
6 years of improvement and investment in infrastructure raised a lot of poor farmers and small, rural town economies into a more comfortable middle class with opportunities they didn't have under Russian Oligarch influence before - so the population wasn't willing to return to Soviet satellite peasant status.