I think you might be basing this on some very misinformed information, even wishful thinking. Russia is not short of resources, far from it, nor are they challenged to destroy Ukrainian advances, they are using weapons way in advance of things available to Ukraine or the West, weapons developed when the rest of the world was effectively standing still on weapons development, and techniques of massive power to draw Ukraine into "cauldrons", so as to most effectively destroy their offensives.
Even the "Wagner Mutiny" was just another ruse, to draw in yet more Ukrainian forces to the slaughter, according to folk claiming to know more about what Russia is doing.
I wonder how long it will be, and how many more Ukrainian lives are going to have to be sacrificed, for us the West to learn this?