This line of reasoning is exactly why everyone bordering Russia is preparing for an invasion, and why no one deludes themselves with "Mr. Hitler will surely stop at Poland." It's not about NATO, ethnic Russians, or any other common excuse, but a fundamental collision between an imperialistic view of the world (represented by Putin's dictatorship) and a cooperative one (represented by the EU). Nations are naturally drawn to the EU, which does not force them to live under someone's boot, and Putin tries to stop that through raw violence.