Shankar, I question this as Putin's key motivation. Although it could be presented to the Russian population as some kind of achievement.

Putin is essentially a mobster boss. Ukraine was there to be subjugated and paying rent (small Moldova, the same). When Ukraine wanted out from this relationship and did not come to heal with Putin's threats, he then tried punishing it into submission. With punishment not working, Ukraine had to be killed.

Real mob stuff.

You're accurate that now he discovers that he can't kill Ukraine completely, he is forced to settle for next best and kill the parts of Ukraine he thinks he can.

Good perceptions. Many thanks.