I grew up in the Cold War so I have an innate distrust for the Russians. I believe Putin, ex KGB, measured the resolve of his enemies and determined it lacking. He / the Russians probably engineered the turmoil in Ukraine as a pre-fab excuse to invade. After seeing how Iran and North Korea BSed the US, he gambled that the worst that will happen to him is a strongly worded statement. I suspect he’s right
Here is the problem that Ben Judah overlooks. Putin's thinking can be characterized as "fuhrerism". He thinks that the western elite are leaders and measures accordingly. He discovers that they do not have a fire in the belly for democracy, human rights etc., -- and they don't, -- and then he concludes that he can bend them at will. That does not follow: the West is governed not by leaders but by managers that obey their own rules in their official conduct. He may yet get his comeuppance because Europe is not going to tolerate another cynical anschluss, -- they know their lessons from the first one.