Earlier quoted context omitted.
Russia invaded Ukraine for basically no reason, it still happened. If you have enough fervent nationalism in the population and an authoritarian government, lunacy isn't going to stop anything.
Russia invaded Ukraine over control of the ports of Sebastopol and Odessa, and over control of the Varangian Road from the Black Sea to Moscow. These are immediate national security concerns. There were those of us who looked at the Eastern expansion of NATO with great concern, a proxy war was going to be fought, and Europe was going to have to deal with the refugees and the political instability.
And calling this a proxy war is, of course, the usual Russian excuse for why they are doing so badly against Ukraine. They really want to imagine that they're against NATO instead.