I think they are going in for the kill while Russian forces are in disarray in the south.
The Kerch Bridge is still closed. If they can cut the supply lines in the northeast, then the Russian army as a whole will be nearly cut off, or at least its supply lines will be extremely strained. Their fleet is stuck inside Sevastopol harbour. Things look bleak for them. On top of everything, I hear there is a plague of mice where the Russians have prevented the harvesting of crops. Even Ukrainian mice are active in this war.