Can't Putin just admit that he fucked up
Honestly, this has very little to do with Putin.
- this war has been going on for almost 8 years; it's not like this is something completely new
- this is, in essense, a proxy war between NATO and Russian Federation
- Putin tried to join (and/or ally with) NATO during his first and second terms, to no avail[1]
- Putin stopped pro-russian forces from expanding to Kharkov in 2014, most likely out of fear of sanctions and/or due to agreements with EU/US leadership (the gravest mistake, imo)
- ukranian government was determined to take the Donbass region by military force, consistently undermining Minsk agreements (due to both internal and external pressure); around a million inhabitants of Donbass obtained russian citizenship since 2019, thus it'd have resulted in full-scale war with Russia in any case
- obviously, any major aggression towards Crimea, with its overwhelming russian majority and russian navy bases, would result in a full-scale war too
- US wants to hinder Russia-EU economic cooperation[2] (to keep EU states in its sphere of influence and to ship its own liqufied natural gas to europe); major russian-european gas pipes go through the territory of Ukraine, and NordStream-2 was about to start operation when the tensions around Donbass had risen
- Russia needs a buffer between itself and NATO military on its western border; thus Ukraine joining a military alliance which declares Russia its primary enemy isn't an option, and Russia's soft power attempts to keep Ukraine neutral have failed (due to obvious superiority of western soft power capabilities)
tl;dr: current military escalation could've been prevented only if a) russia acted more boldly during 2013/2014 crisis AND b) US leadership would've allowed more sovereignty for european nations (imo)
[1]: these efforts effectively ended with Georgian-Russian war, which, curiously enough, was also timed to coincide with the Olympics; even EU (not exactly a pro-putin actor) admitted the military operation was started by then-president of Georgia Saakashvili, a US state department affiliate, who was later wanted for criminal charges by the georgian government and stripped of ukrainian citizenship by Maidan govenment of Ukraine
[2]: see e.g. RAND_RR3063 (2019) report, which outlines pretty much all the events we've seen unfolding in the recent years: attempt at regime change in Belarus, tension in South Caucasus (armenian-turkish/azerbaijan war), attempted coup d'état in Kazakhstan in Central Asia, etc