most of europe voluntarily accepted it not by the sword.
"most of europe voluntarily accepted it not by the sword."
I am not so sure about that, in a time when Christianity was the state religion and people were persecuted if thought to be "witches" and so forth. Early American history even shows persecution of people who didn't tithe or attend church. I have an ancestor in my genealogy who was jailed for not tithing the church, and for preaching on the street corner that churches were not necessary as an intermediary to God.
The victors always write the history. But I do believe many accepted Christianity by at first allowing Jesus into their pantheon. Also, time and scientific progess cured many of their superstitions. Then Pagan rites, rituals and holidays were integrated into the church, making the religion less foreign, and palatable to Europeans. If you examine early Christianity (Gnostics) you'll see these folks were very Pagan. The religion evolved in that area with time, as it did in Europe.