World War II more so than the Great War. The former basically destroyed most of Europe, displaced millions and resulted in the massive collective traumas from deportations, mass murder, carpet bombing, etc.
Brutalism really only emerged in the 1940/1950 after WWII.
That question has an obvious answer : those architects are better at architecture than normal brain architects. Architecture is mainly functional, not esthetical
Aesthetics take the backseat when a two-digit share of your population has no roof. People these days tend to forget that these buildings replaced shanty towns.