A bit left field this, but trying to grope through the murk I wonder if all this was an attempt by Putin to preempt a coup (real or imagined) or similar, as there's an awful lot that doesn't add up militarily. Clearly the invasion of Ukraine was and is an existential problem for that country, but is equally so for Putin. He can't afford to lose or he is toast, so what drove the man to order an attack when it wasn't necessary and carried risks for his entire empire.
The question therefore is why did he invade when the army was so obviously unprepared for a war? This is the real conundrum because he might be a psycopath, but he isn't stupid. The accusations of widespread genocide and Ukrainian attacks on ethnic Russians are patently fictitious to all, so what caused him to need a pretext for going in? After all, armies do not decide to invade a neighbour on a whim because these things take weeks and months of meticulous planning, yet here we are with soldiers apparently expecting to go for an afternoon walk and an army with no apparent sensible logistics organisation, this despite the fact they had just been on exercises - which are precisely what you use to iron out problems and join the dots. The whole episode is suggestive of a snap decision by Putin with no input from his generals, two or three of which have been dismissed and arrested in the last month, though I don't know how many are retired in this manner on a regular basis. Whatever the failings of the Russian army in terms of delegating decisions downwards to the man on the ground, it beggars belief that the generals would be collectively blind to the planning necessities of a military campaign. which again points to a decision about which they were not consulted.
To paraphrase Lady Bracknell, 'To lose one general may be regarded as a misfortune. To lose seven looks like carelessness.' Estimates of Russian casualties are speculative, but a US estimate says around the 7K mark. Too lose 7 group commanding generals, not to mention a significant number of officers commanding the various constituent units of these groups from such a low total just doesn't make sense. Even if the overall losses were 50% higher, it would still seem like a stitch up.
I think something spooked him because the Russians had 7 or 8 years of experience dealing with the Ukrainian military in the east and even with Russian backing on the ground in Donetsk and Luhansk the separatists had ground to a halt. Why did he take the risk that threatened his position?