“Putin has started WWIII and this little punk thinks Russia will survive.”
Yes, as a matter of fact, Putin crazy enough to gamble on the Russian civil defense measures to ensure the survival of enough of the populace to serve as a deterrent against the U.S. risking the Russians going nuclear in a direct conflict. Moscow very ostentatiously publicized how the bomb shelters have had their doors and their stores prepared for immediate use as a threatening signal to the West.
Putin is not crazy.
His Crimean invasion is not economically sustainable without a land/truck route from Russia to Crimea. That is his objective.
The rest is a diversion and a tactic to eliminate the Ukrainian air force and deplete the Ukrainian military supplies and morale, before he makes his land grab.