Part of this is a not-yet-had conversation in here about the deep-seated, centuries-old nationalistic tendencies among European countries to think and do stuff that largely isn't perceived/understood by Americans. I'm no Europolitik expert (though I did sleep in a Holiday Inn) but I've traveled enough in Europe to know that there exists these unspoken nationalistic tendencies, driven by almost ancient zeitgeists. And though the younger generations might seem to be less autonomous in their world views, I think a lot of it still comes into play even for them. I.e. when I said to my Hungarian grandmother in 1989 that Eastern Europe (and Hungary) was finally (sorta anyway) free, the first thing she said is, "those goddamn Romanians are going to try to take us over!" and she had been in the USA for 60 years at that point. I don't think it's just racial or ethnic hatreds (though that's part of it), I think some of it is some sort of self-identity or something. This might explain in part why Germans don't seem to be too worked up about all this, or even that Ukranians weren't all that outraged before the invasion (I heard a lot of "Russians are our cohorts, they won't attack us") etc. It's a conversation that isn't easy to pinpoint, but sometimes Euros act "weird" to Americans (never mind vice-versa), hence the Italian P.M. sending out that "well, except for ..." memo. I think Putin knows this sense of fierce European autonomy and gambled that that, not NATO, would be the ruling sentiment. Perhaps he was somewhat right, I don't know. But I think Europe sort of fatalistically doesn't see this as shocking as say we do.
Now if they go into a NATO country, all bets are off, and Russia will cease to exist while inflicting little damage back - unless somehow they get China onboard militarily, which I don't see at all at least now. IMHO about all this, anyway...