Many of our Christmas, Easter, and Halloween, or All Saints Day traditions are the result of a brilliant bit of marketing by Pope Gregory I in A.D. 601.
He recognized that Christian missionaries were having trouble getting converts when they attacked the local religious traditions head-on.
Gregory suggested adopting the local beliefs and customs into the Christian liturgy instead of trying to wipe them out.
For example, if the locals worshipped trees and eggs, it was easier to bring those objects into the Christmas tradition than to convince the locals to give up their beliefs.
Missionaries even made up church holidays to compete with the holidays of a local religion, for example, All Saints Day was invented by fourth-century missionaries to rival the Celtic holiday Samhain, and its mythology slyly designed to portray the rival Druid gods as devils, spirits, and witches.