Short Answer 
During the French Revolution, the state seized properties from the feudal aristocracy and the Catholic Church, declaring them as national property to shift away from feudalism. The sale of these properties aimed to support the economy and provide relief to the poor, improving living conditions for the underprivileged.
Step 1: Seizure of Properties
During the French Revolution, the state seized various properties, including the château de Villers-Cotterêts. This action was taken against feudal aristocracy and the Catholic Church, whose estates were viewed as symbols of oppression and privilege.
Step 2: Declaration as National Property
These seized properties were declared national property, which meant they were taken out of private ownership. The government aimed to manage these assets collectively, signifying a shift away from feudalism and toward a more egalitarian system.
Step 3: Economic Support and Social Relief
The primary goal of selling these national properties was to support the economy and provide relief to the poor. The generated funds were intended to improve the living conditions for the underprivileged and boost the revolutionary economy.