There is a big connection between purification and animal sacrifice in the Torah. For example, a Jew was rendered impure by handling a corpse. The only way to purify was with the ashes of a red heifer that had been sacrificed at the Temple. Since the Temple is destroyed, all Jews are considered technically ritually impure. However, they keep to the purity requirements because it is God's law. It's also why traditionally a Cohen could not enter a cemetery and why their family are buried near the walls. It's so that they can still visit the graves of their loved ones without entering the cemetery.
When Hyrcanus III destroyed the Samaritan Temple in the 3rd century BCE, the Samaritans got revenge by leaving corpses in the Jewish Temple's Holy of Holies. It took a full year to purify the Temple, during which all Jewish Holidays were suspended. It's interesting to note that even today, Samaritans still practice animal sacrifice in Gaza.
But living sacrifice still plays a part in the Jewish faith as well even though it hasn't been practiced in almost 2000 years. Some nutcase wealthy extremist Jews and Christians put money into breeding red heifers alongside trying to get the Temple rebuilt, since these are believed to be signs of the Messianic Age.
Every year at Yom Kippur in Jerusalem, a few Jewish extremists will try to sacrifice a goat on the ruins of the Temple, but the police stop them every time.
So really, Christianity appropriated something that was already there in Judaism. But what else would you expect from a religion that originally started as a Jewish Messianic movement. It's not something they pulled out of thin air.
Good explanations.
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In simplicity, utility. Through utility, simplicity.