One reason for the French revolution was the prevailing feudal system. 18th century French society was divided into 3 estates.
The first estate was the clergy, second estate the nobles and the third estate was everybody else. The first and second estate owned most of the land and also didn't pay taxes. The third estate, which were mostly peasants, had to pay all the taxes.
Due to France funding the American revolution, and lavish spending by the court, the Treasury was soon empty. This, along with crop failure let to rise in prices and taxes.
Since the poor peasants were the only one who payed taxes, and the rich clergy and nobility did not, it led to tensions.
This, along with many other reasons, led to the French revolution.
