When it emerged, Christianity had to adopt the rites of a religion, and for this the first communities were inspired by the cults that they had around them.
That is why the similarities with the Mithraic rite are so clear, a continuation of Persian Mazdeism, which venerated the image of the divinity Mithras, a symbol of the sun and light as Mazda was (it was not for nothing that a light and bulb company chose this name) in Zoroastrianism.
The priests of this belief were celibate like the Christian parents, and the faithful, who were also called brothers, communally consumed the meat and blood of a bull during sacrifices. They were baptized with water, they fasted periodically and their moral system was almost identical to the Christian one.
The Catholic patriarchs themselves admired such resemblances. Saint Augustine himself recounted that on a certain occasion a priest from Mithras revealed to him that in reality they both practiced the same religion.