Ukraine and Russia in Historical Context.What Caused the War?

In which John explores historical and political context to understand what caused the Russian government's invasion of Ukraine, and how we arrived at this awful now. There is a LOT of misinformation in comments, so why not read directly from SOURCES? But first, CORRECTIONS:

The official language of Ukraine is Ukrainian. "National languages" as a phrase was confusing. I should've just said that 30% of Ukrainians speak Russian as their first language. Also, the etymology of "Ukraine" is not settled as "borderlands." Many Ukrainian linguists argue that the etymology of Ukraine comes from words meaning "In My Land," not "borderlands." Thirdly, I misspelled Kyiv as Kiev. If I made further mistakes, let me know and I'll amend here.