Remember when Wagner marched on Moscow and easily took Rostov-on-Don? The Putin regime panicked and in an act of desperation destroyed its own highways to stop Wagner's advance. That's when it became clear that most of Russia's military assets had been sent to Ukraine instead of being reserved to protect the homeland.
They may still have enough to push back the Ukrainian offensive. But this makes it clear that Russia has never seriously feared a NATO invasion. That only served as a pretext for its useful idiots in the West.
The emperor has no clothes.