Blaming greed is like blaming gravity for a plane crash. Gravity is always there as is greed but that doesn't explain what went wrong.

The federal reserve inflated an unsustainable boom throughout the 1920s which caused a stock market bubble. Artificial credit expansion always leads to an inevitable bust. It's economic herion. It feels good when you first inject the drug of cheap money but eventually reality has to hit and it comes crashing down. Very similar to the housing market crash of 07-08 and the dot com bubble of the late 90s.