Hoover provided investment capital with the RFC and the companies sat on the money, what businessman would continue producing products that no one is buying? Of course the investers could insist the factory keep producing but what investers would do that? Why did farmers dump their milk in ditches when people wanted the milk? The farmers had the product, no investers needed, but it went into ditches. Why would companies spend billions on advertising to create a demand if demand wasn't a major factor?
The problems began with the stock market crash that wiped out investment capital and forced businesses to close their doors and liquidate assets to try to pay off their debts. This is what produced the unemployment you are talking about.
Once the economy had reached this point, there was no way I know of to quickly return it to its former prosperity, however, if Hoover had been able to immediately flood the country with emergency rescue loans to businesses that had had their debts called in, many businesses would not have had to close their doors and lay off their employees and it is likely that the nation would not have suffered nearly so terrible a depression, but the federal government lacked the financial tools necessary to do this on a large scale in those days.
If Obama had made government loans available to all credit worthy businesses and individuals that had been turned down by the banks when the troubled banks started cutting back on lending in 2009, we might well have avoided the recent recession and by now, be enjoying a more robust economy. Instead, Obama tried and failed to revitalize the economy by increasing demand through his stimulus bill.
Not too long ago, both Sweden and Japan suffered financial crises brought on bursting real estate bubbles just as we have, and the two countries responded to their crises in strikingly different ways and had strikingly different outcomes. Japan tried to revitalize its economy by increasing demand through large scale deficit spending on infrastructure projects just as Obama did later, and as long as the deficit spending continued, unemployment fell and the gdp rose, but when the debt reached unsustainable levels and Japan was forced to reduce its deficit spending the economy fell right back into recession and stayed there until Japan finally restructured its troubled banks, making capital more easily available to private investors and the private sector economy finally began to grow again.
In Sweden, the government immediately took over the troubled banks, removing their troubled assets and resupplying them with cash so there there was never a time when credit worthy borrowers did not have the access to loans they needed and the recession that would surely have otherwise followed their financial crisis was prevented. In both cases the key to recovery was ensuring the private sector economy had adequate access to capital,and in no case was the private sector economy ever revitalized by deficit spending to increase demand alone.