20%????? That is huge & scary. Had no idea the percent was that high.
Wikipedia says the Moslem population of France, as of 2015, is 5% to 10%. I will note that’s 100% variance, but it’s still, at most, 50% of 20%.
However, Wikipedia also says that only 33% of French citizens believe there is a God or life force or higher power or some kind of spiritual something or other. Even allowing for the crap one gets from survey results and sampling, one can reasonably believe that a surprising number of those roughly 1/3 who have some kind of God-thing going on are Moslem.