I think [0] Putin vastly miscalculated public sentiment in Ukraine. His attack was based on the premise that Ukraine's government is essentially a puppet state

I think [0] Putin vastly miscalculated public sentiment in Ukraine. His attack was based on the premise that Ukraine's government is essentially a puppet state of the west with little popular support in the country. This is been how the Russain state has been telling the story since 2014. He probably expected this to go like the Taliban's expulsion of the US from Afghanistan in 2021. Most of the people would support, or at least not be too bothered by it, the government would flee, and the few government supporters would have no will to fight. Then he could install a sympathetic government as there is in Belarus. But obviously, popular support for the Ukrainian state turned out to be much, much higher than Putin thought. As they say, don't get high on your own (propaganda) supply. [0]: With the obvious caveat that I'm just a random person on the internet with no special information.