Why was there instability in French government 1791-99?

It is the most radical and violent period of French Revolution. It followed the death of king Louis XVI who was guillotined in Paris. The radical party of the Jacobines took control of the National Assembly. Terror and repression were extensively used to crush real and suspected enemies. War was fought against Austria and Prussia where the revolutionary government thought emigrés were plotting against the republic. Many executions were carried out under orders of Maximilien Robespierre, head of the ruthless and feared Committee of Public Security. Many leaders of the revolution were guillotined, even Robespierre himself. Those were times of chaos and uncertainty in France. The 1799 coup d'état of Napoleon put an end to chaos.