Answer:
they caused banks to stop lending money to businesses
Explanation:
Many businesses entities that exist in 1920s - 1930s relied on the money supply from banks due to the economic damaged that's caused during the World War 1.
When the banks started failing, the businesses lost the ability to obtain credit that they can use to sustain their operation. As a result, this create a ripple effect that massively reduced the economic productivity and job opportunities in Untied States.