I always thought Paris was the “City of Light” due to lights of the Champs…

And here is has to do with the Enlightenment and the brilliant people living the city:

Paris has many nicknames, but its most famous is “La Ville-Lumière” (most often translated as “The City of Light”),[15] a name it owes first to its fame as a centre of education and ideas during the Age of Enlightenment, and later to its early adoption of street lighting.[16]

[From Paris – Wikipedia, the free encyclopedia]