Lack of jobs for a decade and a half in the Great Depression. What could have slowed the economic recovery that started to appear a few times?
Amity Schlaes provides a quick summary in her Forbes column, Roosevelts versus Plutocrats, in which she also describes the slant and bias in the new PBS series on the Roosevelts.
After the turn of the century, Teddy Roosevelt started his war on big business by going after railroads and coal. The railroad industry was already weak and the litigation toppled a tottering industry. The far less regulated trucking industry made sure rails never recovered.