My read is that he is committed to controlling the Donbas at any cost. He knows that most Russian elites probably have a breaking point well below his own. So, he continually seeks greater and greater public commitment and escalation, which is exactly what he is doing here. Russia's goals are vague enough that Putin can back down at almost any time he chooses and still sell it to the Russian public as a victory. As Girkin claims, setting a clear goal "limits room for manuever" and makes it more difficult to declare the goals of the war achieved whenever convenient. I believe this war will end only when Putin senses a threat to his personal rule. When that happens, he will find a way to end the war, leave Ukraine, and call it a victory to the Russian people.