That relies on the assumption that what’s good for the economy is good for the capitalists, they always make sure that capitalism occasionally goes up in flames to take advantage of social unrest.

That’s the point.

In Germany there was a battle between left and right back then. The economy boomed in the 20s and faltered in the 30s. Capitalists saw the threat of socialism looming just behind Poland and so they supported fascism.

The Nazis funneled billions into large businesses. It was unsustainable and morally multi-level wrong, but they skimmed a lot of profits from these agreements. They got rich, while the economy started to collapse - even before the war.

Even after the war, most of them got away. They kept much of their wealth.

In fact, fascism often gains support from middle class desperation, with the blessing of the booj who prefer it over communism (which tends to rise from the lower classes during similar times of desperation)