There was the whole problem of automation in manufacturing.Machinery had forced people off of the farms and by 1925 it was forcing them out of the factories.
The idea that companies were profitting immensely was true, but the general working population was hurting.
Not only were jobs lost to machines but the newly unemployed were willing to take your remaining jobs for less money than the people still working.
Employers drove general wages so low that people could not afford houses or even shoes.
Of course now they had factories able to produce like never before but they had nobody able to buy their products.
The result was a sudden drop in profits.
That is what triggered the sell off of stocks as people tried to cover their losses.
The business people called it *overproduction* and shut factories
So now the factories shut unemploying more people, who underbid each other for what jobs were left. Which meant they could afford to buy even less, which meant more jobs lost etc etc.
This problem was encountered in every industrialized nation.
It was not until they increased wages and cut back hours that things improved really.
Yes it is true that the WW II soaked up a lot of the unemployed, and got the factories producing again but it would have collapsed into the same mess all over again after the war without the wage increases and reduced hours.
We appear to be in much the same situation today as was seen in the 1920s.
On other feature was that the rich suddenly faced taxes that they had never experienced before during the 1940s.
This was done to bring the levels of wealth concentration down.
We are also seeing the similar levels of wealth concentration as existed in the late 1920s and 1930s.
So the problem was not the lending system that caused the depression. The problems were much more fundamental and are a basic problem with classic capitalist theory.
Think of a Monopoly game. Early in the game everybody is buying and selling, the money is changing hands, but at the end of the game one person owns everything and there is no economic activity of any sort.