Putin’s already raised interest rates to 20%, which means that as increasingly worthless as rubles are to the average Russian he’s also calling more of them back into the treasury. Put another way, thanks to his war the ruble is going to be garbage in terms of purchasing power but he also will want Russians to hold less of them so he can put the garbage toward building more weapons. If this goes on long enough he’ll also start issuing war bonds and raising taxes.
His vision of “Russian economic self-sufficiency” isn’t too far off from that of North Korea (or Orwell’s Oceania): a closed economy with money that’s worthless to the outside world and that is in short supply to any citizen who isn’t a corrupt government official, high-ranking guard labour thug, or defense contractor executive.