I don't want to derail that other thread so I'll drop this here instead:
TheLostBigBoss
It was actually due to WW2:
https://www.demos.org/blog/5/25/14/piketty-has-two-separate-income-inequality-theories
The greatest wealth distribution scheme of the last century was, in fact, an apocalyptic world war. We are actually headed towards a repeat of those economic conditions that appeared in the early 20th century, except this time it's driven by global socio-economic chaos (as a consequence of climate change and decades of austerity) instead of imperialist Germany.
An apocalyptic war... which never reached the borders of the US
Your chart is US wealth share, yet you're talking about the economic factors of Europe.
WWII was definitely a major reason the middle class had such an insane boom, but your thesis seems to be off if your arguing absolute destruction was the prime cause of wealth distribution in the US.