Damn. I just actually understood the syllogism driving Putin's obsession :

the special operation revealed that not only the political leadership in Ukraine is Nazi, but also the majority of the population. All Ukrainians who have taken up arms must be eliminated - because they are responsible for the genocide of the Russian people

Putin, before the "special military operation", spoke of the necessary denazification of Ukraine, but also of Ukrainian genocide against Russians. Apparently the logic works like this :

• The nation of Ukraine fundamentally does not exist
  
• They worship Bandera (arguably, but he was named Hero of the Nation in 2010), who was a Nazi
  
• THEREFORE they are Nazis, and inherit the moral responsability for the genocide against Russians in the Great Patriotic War.

It all makes sense, finally. For a while, I was worried that Putin was clinically insane.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}