Russia can’t commit its full army to the war, for quite a few reasons. One of which is that it’s “full army” has been decisively proven to be WAY more of a paper tiger than anybody would have guessed.
The scale and duration of this war are orders of magnitude are far larger than anyone in Russia was planning for in January of 2022. They discovered that their battalions were rife with ghost soldiers so the officers could scoop up their pay. They discovered their modern tank stockpiles were not only unmaintained, but also often scavenged for parts to either repair other vehicles or simply sell on the black market. They discovered that, incredibly, their Air Force was unable to fully suppress a force that (on paper) was a mere fraction of their size and supposed capability.
This is scratching the surface. This shit goes way deeper, and it involves their whole military industrial complex, as well as pretty much all seriously profitable ventures in Russia. If money is made at any serious scale, someone’s going to put together a scheme to take a cut of it. That’s how the country works. And it’s biting them in the ass right now.