Going back to Vietnam War days I wondered how a nation can bomb another nation and not expect payback on their own vulnerable citizens. These terrorists attacks are due to France being involved in bombing against ISIS. We may despise ISIS grossly but they are a result of Western policy failure in the invasion of Iraq and the Western powers drawing up the boundaries after the collapse of the Ottoman Empire after WW1\. I never felt comfortable with so many nations bombing populated Syria and Iraq knowing that many ordinary citizens will be sure to be killed and infrastructure destroyed. Seemed completely wrong a George W Bush type of response.
France opposed the invasion of Iraq. They did not participate.
As for ISIS, well quite clearly the international community cannot stand back and let a depraved group of terrorists rape and murder their way across two countries, committing genocide and all the while threatening the international community. France's role in this coalition was minimal until they were attacked last year.
The actual reason France was attacked is because they have a large and disaffected muslim community on their soil, who see the French people as infidel targets. The exact same reason that terrorist attacks have taken place in Brussels, the UK, US, Australia, and practically every country with a sizeable muslim population.
No need for in depth analysis when the answer stares you directly in the face.