Well, the Nazis are disgusting and something Putin can point to for PR during the invasion, and they are a real problem in Ukraine, but Lance is right: the real reason Russia is invading is certainly because of the geopolitics involved, not because of the Nazis. Not exactly "let's rebuild the Soviet Union, let's land grab," but more about the security of the country.
Take a look at Russia's western border below the Baltic Sea: you've got Estonia and Latvia, both members of the anti-Russian military alliance NATO along with Lithuania.
Then below that you've got Ukraine: they had a president in Yanukovic who was friendly to Russia, and then when some organic protests sprung up in western Ukraine, the West took advantage. Despite the fact that Euromaidan was primarily popular only in western Ukraine and hovered at around 45% approval in the country, the democratically elected president was deposed and replaced by people friendly to the West. The United States and other western governments were directly involved in this overthrow, and were caught on tape selecting the new leadership of Ukraine (
https://en.wikipedia.org/wiki/Victoria_Nuland#Leaked_private_phone_conversation). How would you feel if Russia oversaw a revolution in Mexico and picked out the next leaders? Would the US invade Mexico? I think it would!
South of Ukraine is Belarus. The US and the rest of the West have been trying to "Guaido" Belarus, simply recognizing an alternative leader, pretending that is the actual leader, and then sanctioning the state and its people into poverty to attempt an overthrow by mass suffering. Say what you will about Lukashenko, and I do not think Belarus is a real democracy, but there is no chance that the Belarusian Guaido, Sviatlana Tsikhanouskaya, won that election, or that the west should be able to dictate to another country who their rightful leader is. But now this completes the picture of the attempt to turn Russia's full western border against them assisted by operatives and influence from the West (although it has not succeeded in Belarus, much like it has not succeeded in Venezuela at anything except increasing the suffering of the Venezuelan people).
So this is the picture we have, the geopolitical situation, with now discussions of Georgia (to the south) and Ukraine joining NATO against Russia simmering in the background, where Putin and Russia decide "enough" and to invade. Putin is not a madman, and the invasion is an entirely logical attempt to recreate a neutral buffer zone outside of Russia, from where both Napoleon and Hitler invaded their country. It is an affirmative act of aggression, it is wrong in many ways, and it causes suffering to the people in Ukraine. The Russian system is not any better than the Western one politically; there is no reason to believe a Russia-dominated world would be better than a West-dominated one. But it is an entirely logical move that Russia has made from their own perspective and for their own interests. It is a sign that the we are returning to a more multipolar world, akin to the Cold War, rather than the long US-dominated hegemonic world order. That is most likely a good thing, because it will make the exploitation of countries around the world by the United States more difficult. The clearest and most interesting thing is that China is peacefully rising and will probably become the new preeminent superpower of the world. While they are a largely capitalist country too, they are also assisting with the development of southern nations around the world on much better terms than those countries have ever gotten before.
