My grandfather explained the Great Depression many times to us grand kids ad nauseum over and over. His cab business went bankrupt in the 1930s. Apparently in a depression almost everyone walks. I considered him an expert having almost been ruined by it. He never mentioned trade once as a cause or having anything to do with the Great Depression. He did talk about stock speculation on borrowed money.
My grandparents explained the Great Depression this way. If you had spent all you had, you could get help, from charity and government programs. If you had even a little bit, you got nothing. When the banks finally settled the depositor’s accounts after the bank failures, people got ten percent on their account. For my grandparents, it was enough to buy a child’s coat. Life savings gone, wiped out, but the kid got a coat.
The stock market crash certainly was a factor in causing the Great Depression. Other factors, bank failures in the midwest due to droughts, the failure of a large bank in Austria, the rise of Hitler, almost a perfect storm so to speak, a convergence of many factors. Also, mixed signals from the federal government, Smoot-Hawley, inaction from the FED or counterproductive actions from the FED etc. etc.