Answer: Their rivalry with Britain and the Enlightenment ideas of the population
Explanation:
The French and the British were rivals at the time of the American revolution especially after the culmination of the Seven Year War which saw the British emerge as Europe's strongest naval and colonial power. France therefore wanted to weaken the British and their influence and so saw the American Revolution as a way to do so.
At the same time, the common population of France also supported the revolution because they were believers in the ideas of Enlightenment which called for the liberty and freedom of all men. With the support of both the people and the Government, France was therefore made a very likely candidate for foreign aid to the Patriots.
The Revolution was quite expensive for France however and was one of the reason the monarchy was overthrown a some years after the Revolution.
