Because you literally cannot maintain a military without a functioning economy. It is impossible. Please explain how Russia, with a collapsed economy, will be able to maintain an army of any size.
Or do you mean how am I sure the Russian economy will collapse?
Well it was circling the drain BEFORE the war. Russia cannot compete except for its grain, oil and gas exports. They were about the only thing keeping the country afloat. Now no one is buying the grain, no one is buying the gas or oil, and the Rouble is tanking. The Russian financial sector is on the brink of collapse already, with its own financial analysts saying it could implode literally any day. The banking sector is already having to fight fires to avoid a run on the banks, which gets more and more likely the more worthless the Rouble becomes. When your country cannot import goods because no one wants to sell to you and you cannot afford them anyway, you then become totally reliant on whatever you can produce from within your own borders, but eventually your economy becomes so crippled you cannot afford to pay your people. It's no good having huge fields of wheat when your farmers wages mean they can't afford to buy bread. It's no good having gas fields if your gas workers can't get paid. Eventually, your country collapses completely.
