What I believe is that he had no idea, not being a strategist, that the advice he was receiving was as rotten as his short-term army. When it became obvious that all he could do was batter it to the ground, as he has other cities, For him, Kyiv is the birthing cradle of Russian culture. He's written extensively on it and Ukraine's right to exist, other than as a dialect region of Russia. I don't think he's given up on acquiring it long-term, just not by this operation. He can declare it "victory" at any point now, if, as you say, he can hold on to his gains in the south. One thing's for sure. Ukraine is not safe so long as Putin lives...