The frogs bred for consumption are typically bull frogs or pig frogs. These are not the endangered frogs. Endangered frogs are tiny, their entire body weight is probably less than a single leg of a bull frog and its not commercially viable.
The endangered frogs are native to places like South America, where they are suffering from a loss of habitat and from chemical pesticide/herbicide run off from farms that are killing them off. In other regions they also suffer from light pollution.
I doubt its that the French are to blame, especially when east asia has a huge consumption of frog legs