Marie Antoinette has a very famous line "Let them eat cake" related to the food
crisis in France. Why do the people of
France have no food?

Poor taxation on the upper class.

Explanation:

The French typically taxed the lower classes 90% of the government's taxes, while the middle and upper classes typically only had to pay 10% of those taxes. Though, the lower class who were depended on the taxes were barely working and had very bad living conditions.

Due to these poor conditions and heavy reliance on a class that could not fulfill these wishes, food shortages occurred due to the lack of money coming in. The lower class could barely live for themselves so it was out of question that the lower classes could aid with taxes.  

the commander in chief