What caused the Great Depression?

Since the New Deal, most history texts will agree that the Depression was caused by "wealth inequity" and only by the benign munificence of the federal government was this injustice corrected after the crash.  However, this appears to not account for several factors.  Firstly, at the conclusion of World War I, the US was the only major industrial power not severely weakened by the war.  The unprecedented industrial growth to produce war materiel switched to the domestic market for consumer goods, resulting in an overabundance. This was the era in the US of the "Roaring Twenties," where the economy continued to expand after the war and the standard of living for both rich and poor increased, but it was an "artificial high" due to the war. Secondly, because of restrictive tariffs imposed by government, trade with foreign nations, and especially Europe was disrupted. Thirdly, postwar Europe suffered from the effects of the war, US tariff policy, and Germany especially went through a period of hyperinflation due to the harsh conditions of the Versailles Treaty, which effectively destroyed their economy.  Finally, abusive investment practices, where individuals (such as JP Kennedy, father of the President) would manipulate the stock market, causing huge amounts of money to flow in an out over a short time created market instability. Today we would call that insider trading. Because the Federal government did not stop the stock market manipulations, but did enforce a restrictive tariff policy, the market crashed, Europe could not purchase US goods for lack of capital, and the US had huge stockpiles of consumer goods that didn't sell.  This brought the US, and then the world's economy to a standstill, and then decline.