Putin is a psychopath who doesn't care about anything. He gets money for the war anywhere he can. If 99% of the Russian economy gets destroyed, he'd redirect the remaining 1% to fully fund the war.
Putin does not have absolute power entirely on his own (no dictator truly does). He can only continue with what he is doing because the Russian population on average either actively supports him or is not working against him.
If literally 99% of the Russian economy was destroyed, no matter how currently oppressed they presently are, the Russian people are likely to rise up and remove Putin. It'll be bloody as all hell but if the economy were to truly and completely collapse (let's say, all refineries were severely hit and taken out of commission for months), it would happen.
> If 99% of the Russian economy gets destroyed, he'd redirect the remaining 1% to fully fund the war.
This is impossible, even in a dictatorship.