it was an adaptation of other spring rituals.
instead of crushing local traditions, christians adopted many local rituals that became traditions over time
They were already traditions.
You can take Easter, which originates in the nordic spring ritual embracing Ostera, the goddess of fertility.
Eggs and rabbits are the Captain Obvious symbols of that.
Or Christmas, which is the ritual of the winter solistice, even the candle ligthed christmas tree as a symbol of the returning sun was snatched by the christian intruders.
They did not know that originally in their palestinian dirthole.
Your Halloween, derived from the catholic Irish "all hallows day", was before the missionaires did their brainwash job a celtic ritual at the end of october, when during the earlier darkness and grey days the souls of the ancestors might have shown up, and people disguised themselvses to daunt them.
It was called Samhain.
For all of this mutilation of traditions over thousands of years I deeply contemn this desert superstition.