Allied forces had formed blockades around Germany during WWI, and in order to make Germany surrender, they essentially starved the citizens.
The economy had crumbled apart, and there was almost no chance of rebuilding it all.
There was also mass unemployment, too.
Germany could not pay the Allies, according to the Treaty of Versailles, and French and Belgian troops invaded Germany to take goods.
This all angered Germans, and in the end, Hitler decided he had enough and took power.