In 1917, what caused the ranks of the French army to mutiny?

The 1917 French Army Mutinies were due to the loss suffered at the Second Battle of the Aisne which was the main action in the Nivelle Offensive. When the troops entered the battle, they were optimistic having been promised a decisive war-ending victory over the Germans by General Robert Nivelle. However, failure to win ruined their mood resulting in the mutinies