Question

Why was the french treasury bankrupt

Answer 1

Louis XIV had made huge state debts by building the Versailles palace and declaring wars (especially with Austria and England) which cost too much money.
When Louis XV entered the throne, there was a state debt of 400 million livres, and he couldn't repay the debts.
He tried to though, by making the French pay taxes (everybody had too, except the clergy and nobility).
It wasn't enough, and when Louis XVI succeeded him all he could do is raise the taxes and hope for the best.

It didn't work out, and France went bankrupt.

Hope this helps!!