It's not exactly true that Russia was the cause of it. At least not fully. I'd share the blame between US, EU and Russia, equally.

Worth watching this for a background of how the whole thing started. The guy was pretty on point with it, and it checks out from other sources too.

UnCommon Core: The Causes and Consequences of the Ukraine Crisis John J. Mearsheimer - The University of Chicago - 2015 https://www.youtube.com/watch?v=JrMiSQAGOS4