That cultural paralysis produced by WWI was really the ground opening up underneath the West’s feet:
And then… And then the story failed. Those we trusted, those in a position to know, sent waves of young men to be slaughtered for not much purpose at all. They sent them to stack ten deep in death and to stink the air so badly with their rotting that everyone in the vicinity took up smoking to dull the sense of smell. Worse, this was reported in papers all over Europe. Worse, people could go to the front and back in almost no time. Worse, yet, was the reports of German atrocities, a lot of it, at that time, made up to incite people to hatred and war. (There weren’t as many nuns in Belgium as, reportedly, were raped by the German Army.) It was all too big and too glaringly obvious. After all, it’s not unusual (though it tends to surprise Americans) for Europeans to have relatives all over Europe, relatives who are nominally foreigners. This was especially true in England with Germany.
It wasn’t the same thing as going and conquering them-over-there no matter how much for their own good. These were people we knew. This was, beneath the superficial differences, our own people.
This is about right. The story was one of progress and civilization. There hadn’t been a general European war in 40 years, hadn’t been a really serious one in almost a century, and people forgot such a thing was possible, and what it looked like. If art and culture are about the human condition, and the basic story turns out to have been wrong, it will lead to a massive crisis of confidence. And I agree, we’ve never really recovered from it.