Why did the Russians divide their invasion into four main groups? They should have known that it was not going to be a repeat of 2014 where they seized Crimea without any resistance. Crimea was Russian so it was never really Ukranian. But Kyiv is Ukranian so why would the Russians seize Kyiv in a cakewalk?
False sense of superiority b/c very few countries have dared to directly challenge Russia since WW2. Plus a tendency to believe their own propaganda. North America has a similar attitude, or we did, until Uncle Joe took the wheel.
The attack on Kyiv was a diversion.
To defend the national capital, the Ukrainians had to leave the Black Sea region with less defense.