This actually came about while Christianity was still trying to convert everyone on the planet. Most pagan civilizations were in the practice of worshipping a horned god. Greece had Pan. Celts had Cernunnos. In order to try to turn these “heathens” to the “righteous” path, they had to make them think that their horned god was really the personification of evil.
Consequently, the reason that Mary is worshipped in Catholic circles is due to similar reasons. While the Christians could turn the people’s heads from many gods to one god, they could not make the people believe that there was no goddess. The Catholics were forced to put Mary upon a pedestal in order to placate the masses.
But that is just my two cents.