I have absolutely no idea what Russia was expecting from their three day special military operation, currently on 3 years, 7 months, and 2 weeks. But surely whatever they were thinking, if I could go back in time and paint them a picture of how the situation is today, they'd jump out the window (or be 'helped' out of them, as appears to be a popular pastime in Moscow this decade). This has to be on the levels quite near 'worst than our worst case scenario'.
I think Von clausewitz's revenge on the russian plan for Ukraine hasn't even begun yet. If Russia ends up wanting to turn lands they currently occupy in lands they annexed (a land that is productive and well on its way to just being culturally subsumed), the cost of that operation will be even larger than the astronomical cost they are paying to gain them: Their utter disregard for Clausewitzian planning means it'll be one heck of an insurgency.
Unfortunately, Russia is one of the most ruthless countries in this regard and will simply massively replace the population, starve it out, or otherwise eliminate any odds of low morale amongst the populace or active insurgency by simply replacing the entire population.
But that also destroys all inherent economic productivity other than natural resources. Russia already has plenty of land and plenty of resources; what they need is more people in general and productive, creative members of society in particular, neither of which you can make happen by starving a population that hates you for how you fought that war and still holds out hope they can drive you out.