From Putin’s Perspective, he’s currently engaged in a civil war, an internal conflict, nothing more – there was never ‘Ukraine,’ just the Ukraine, a wayward province now being reclaimed by its rightful owner: Russia/the Soviet Union/Imperial Russia.
And for Putin this is a war of preemption – the Baltic States, Poland, the Czech Republic, along with other former Soviet client states are all lost and now members of NATO; with democracy extinguished in Belarus, a conquered Ukraine will help establish the necessary bulwark against an aggressive, encroaching West.
The Russian dictator is therefore willing to pay any price, render Russia a pariah state, destroy the Russian economy, none of it matters – the lawless, criminal invasion of Ukraine was no mistake, no miscalculation.