Excellent question. That's why my previous query.....was it just for "show"?
Every religion in that part of the world demanded some sort of sacrifice, meaning the death, generally by bleeding to death, of some animal: goat, sheep, bull, or chicken. The most impressive sacrifice woud be human, but Christianity one-upped everyone by sacrificing a Deity. Communion involves he parishioners, rather than the priests, eating the sacrificed entity.
Ritual cannibalism and deicide are pretty hard to beat.
To most of us in our modern age it just seems rather dumb to bleed a chicken to death to gain the favor of a God, and then, leave it for the priests' dinner. To people back then, it was expected. You can't be saved without some blood being spilled. See what your nasty sin made us have to do?