Why was king Louis xvi tries to raise money on taxing the nobles?

During the Seven Year's War France lost most of its overseas treasure to Great Britain. The resulting ecomnomic damage almost destroyed the monarchy. However, some of the economic was repaired in the 1760's by the minister, the duc de Choiseul. Because Louis XIV and Louis XV spend way to much money and left a huge state debt. Louis XVI inherited that as he accessed the throne (a debt of 400 million livres!) In 1788 the French government went bankrupt.