The word "Mangan" means "fulfillment of one's prayer/request" in reference to the completion of the 33-temple pilgrimage. People who complete the pilgrimage are considered to be superior to others.
And so the Japanese phrase "ta wo nuku" (他を抜く), meaning "surpassing others," applies to them. Since "ta wo nuku" almost sounds like "tanuki," they have all these tanuki here.