A detailed analysis of Russia tank storage
And something Timothy Snyder has pointed out in several places. The core reason for this war is Putin and Russia believe that Ukraine is not a real place, not a real country (there are a number of other reasons, but this is at the core of it). They believe that about all the former Soviet Republics and pretty much anyone else who was once in the Russian empire.
Like a small child who is exerting its influence over the world for the first time they believe that if they once touched it, it's theirs. The idea that Ukraine is a sovereign nation with borders that should be respected doesn't apply to Russia. Ukraine is just a breakaway province that needs to be brought to heel and the rest of the world helping them is interfering in internal Russian affairs.
Russia was willing to play along with Ukraine's separateness as long as Ukraine stayed under Moscow's influence like Belarus has. If Ukraine is playing at being independent, but really is just a vassal state of Russia, that is acceptable. A truly independent Ukraine is a threat to Putin and Russia.
Putin's argument to his people is basically, "yes Russia is corrupt, yes it's a miserable place to live, but everywhere else is worse." He needs people to buy that even if they don't believe anything else. It's the way he stays in power. If people believe life can't be any better, then they won't rebel. What's the point?
A health democracy in Ukraine with a growing market economy runs against everything Putin says. It's more dangerous than a healthy democracy in someplace like Latvia because of the personal ties between Ukraine and Russia. There are a lot of Russians with Ukrainian family. If Ukraine grows into a healthy strong democracy, the people there will tell their family back in Russia and the big lie will be exposed.
The talking heads on Russian TV have been going on about how terrible things are in the west like people in the UK are starving with only turnips to eat (which are imported from Russia). Any evidence of political instability in western countries is magnified and trumpeted on Russian TV as evidence of how everywhere else is as corrupt as Russia, or worse.
Of course the rest of the world doesn't agree with Russia. Especially those who are in territory once controlled by Russia.