Halloween was formerly a Scottish religious festival. Chrsitians kept the external tradition but changed its meaning to be simply fun. In that way pagan Scoits would not realise so easily that their culture was being destroyed. The same was done with nearly all native European religious Feast. The Reborn of the Sun was kept in Christmas, the Summer Solstice was changed by the Sint John Festivity. In all cases the rite was kept but the real meaning was lost.
This tactic used by the Church was so effective that in a short time the pre-Christian European culture was not only destroyed but also forgotten. Not to worry too much about it, after all they just destroyed pagan cults but..... be carefull!!!!!!! The same tactic is used today by leftist and secularists against Judaism. Note that today the anti-Torah, anti-Semites do not only tolerate but even take part in some Jewish Festivals, they may attend Hanuka public menorah lightings and other public Jewish celebrations as far as they are emtpied of their original meaning. They promote "religious tolerance" but at the same time they try to erradicate the real Judaism, Kashrut, Jewish marriage, Shabbat.....