The Stock market crash of 1929 was indeed the cause of the Depression, as the market crash put Wall Street in panic. Millions of the Stock investors lose it all. The lack of confidence in the situation ceased consumer spending; this resulted in massive layoffs of workers.
In general, no, Mesopotamia did not fall because of attack from other empires, since it was primarily due to the Tigris and Euphrates Rivers drying up that led to a lack of produce, and therefore a fall in the empire itself.
Because the public discovered the spread of corruption among the party leaders they were forced to resign
White Sands Missile Range