Because obliterating Kyiv would have immediately exposed the great lie that Putin told Russians:
That all that was required was a 'brief', special military operation, because average Ukrainians were actually Russians, yearning to be free of a Nazi, Ukranian, drug-addled, satan-worshipping government and a battalion of neo-Nazis.
Putin couldn't very well then just completely flatten Kyiv straight out of the gate, and kill all those Russians, keen to shower rose-petals in the path of those Russian saviours, could he?
No, he couldn’t, and that is why he didn't.
He also apparently expected to quickly just 'take' Kyiv and install a friendly government.
However, the sorry state of his corrupted military, its planning, equipment, doctrines, morale, execution, logistics, plus the ferocious Ukranian opposition with NATO weapons, thwarted him.
He had no plan 'B'.
Only the subsequent beatings and retreatings have brought modified, more modest claims, as reflected by his stooges on here, and after all, revisionism is a Russian art form.
Putin initially snookered Ukraine (and the West) when he took Crimea in 2014, and now the failure to boot him out at the time can be redressed.
Ukraine is naturally keen to have it back, energised by its considerable battlefield success, and the fact Russia is still liberally bombing its civilians and civilian infrastructure - and the simple fact that Crimea is apart of Ukraine.
No 'take-backs' or 'do-overs' to reverse Kruschev redrawing the border in the 1950's.
I think history will judge Putin as just 'a bit too smart for his own good', as the saying goes.
