Putin failed to learn the lesson that the only way to ensure you will not be occupying another country, which drains enormous resources, is to not try to topple its government in the first place.
Sadly, this blunder has been repeated throughout history.
Putin will eventually realize that he can’t afford such a costly endeavor, particularly when the majority of his foreign reserves have been frozen.
The Russian economy is far too small to support a prolonged war effort against a brave and heroic Ukrainian resistance.