Hi doma,
I don't see change the way you do.
When Augustine came to the land of the Angles, he encountered a people who worshipped (amongst others) a goddess named Eostre and who had a popular spring festival in her honour. They named the month of the festival Eostre Monath (Northumbrian: Ēosturmōnaþ; West Saxon: Ēastermōnaþ; Old High German: Ôstarmânoth - sorry, couldn't resist the old letters, especially the þ pronounced th) - Eostre's month.
What were the early Christian missionaries to do? Oppose Eostre? Or absorb her?
They did what they always did. They absorbed the festival and gave it a Christian theme. Eostre was remembered in the name of her Easter festival. But the festival of rebirth in the spring time was co-opted in favour of the resurrection of Christ - which was the Christian spring/Passover festival.
Within a few centuries of the conversion, there ends up being a bit of a debate about the dating of Easter between the English/Irish priests and the Roman Church. The Roman/Papal calendar won the battle. Easter in England was harmonised with the Christian resurrection festival throughout Christendom. Or so Bede tells us.
Does this mean that Easter in the Christian tradition is about the worship of Eostre? No. She is long forgotten by most English Christians. But as I think Mark Twain is said to have put it when describing history, religion may not repeat itself, but it rhymes.
| 
