If widespread poverty, inequality, youth unemployment, and misery produce riots, as they “plausibly” just did in England, why was there no comparable violence in the 1930s?

Because the present generation has been taught that they have a right to wealth, equality, employment, and happiness. The Englishmen of the 1930s had lived through the Depression and then had to fight WWII. They were tough people. It’s the same for the US. Compared to my parents, I’m a wimp. I’ve had it too easy.