Halloween originated in the 9th century when Rome couldn’t force the pagans of the British Isles to stop acting like pagans. If you can’t defeat your enemy, join him as the Catholic Church has done since Constantine joined the Church and took it over via government blessing.
All that ancestor worship, spiritualising food during the harvest season, and calling on ghosts to help survive the coming winter—many Taiwanese Christians don’t want to let that go even today.
Seven centuries later, Europe had enough of “pagan Christendom”. On Halloween, Marin Luther nailed 95 theses to a church door and revival began.