If you think about it, he may be clearing out a lot of the Financial Thugs that have stood as a Challenge to his control of Russia. By crashing the money system, and leaving them with little financial reserve, he is clearing the board.
Russia is rich in resources; Putin can use them to re-boot the economy, minus a hell of a lot of Russian mobsters.
Auribus teneo lupum, nam neque quomodo a me amittam invenio neque uti retineam scio.
“I hold the wolf by its ears, for I neither know how to get rid of her, nor yet how to keep her.” – Terrence, c. 165 BC