Because il is a « pronom impersonnel ». Ex: Il fait froid (It is cold). Ça a « pronom » use for replacement. Ex: J’ai vu ce film. Ça fait peur. (I saw that movie. It is scary)
In France, the separated God from government and state so many symbols and subjects in French art do not have Christian or Biblical themes. Some French art might have Christian themes, like some American art, but most artworks after the separation focus more on earthly and human themes.
