I guess what I have a hard time understanding is the part about "...combined with the maldistribution of wealth..." Its very understandable to me that the excessive speculation in the stock market caused a very large bubble, than when it eventually burst, destroyed a huge amount of capital, thereby wrecking the economy. That makes sense.
Not sure how the income inequality is linked as the other major factor. If anything, I would guess income inequality would have prevented the average American from participating in the stock market speculation. He would be grabbing for torches to destroy the system, or maybe feel he didn't have enough money to waste any in the stock market.
However, I thought during this period, the average American truly bought in to the capitalist idea that investment can make him wealthy. I thought it was the participation of the average guy, not his wanting to scrap or destroy the system, that helped build up the bubble.
So I think maybe it depends on who is doing the post-mortem of likely causes. I could see how a free trader would say, " the market crashes, combined with the raising of trade barriers, caused the American economy to capsize."
In other words, pick you favorite political cause, pair it with the market crash, and you get the cause of the Great Depression that supports your world view. You could say men wearing hats, combined with the market crash, led to the Great Depression.