In Beowulf, how do the Roman Catholic monks change the story to a Christian morality epic?
You've asked a really good question. The tension between Christian and pre-Christian (or "pagan," if you prefer) world views is, to me, one of the most interesting elements in Beowulf.
I'm not certain that it's possible to demonstrate with certainty that the Christian author/s (perhaps a monk or monks) who wrote the Beowulf manuscript indeed changed an old Germanic story into a Christian morality tale, but the story does show the differences in the two world views. I also believe it's fair to say that the values expressed by and embodied in the heroes in this epic are largely non-Christian (e.g. the gift-giving and the absence of an afterlife or "kingdom of God") even if the narrator is Christian.
The "Overview" section of the Beowulf study guide discusses this topic in some detail. (See the link below.) In that discussion are two particularly interesting items:
- the use of only Old Testament (not New Testament) Biblical references (for example, Grendel is supposedly a descendant of Cain, and Beowulf's sword is decorated with a depiction of the Flood)
- the rough equation of Fate (a pre-Christian concept) and God’s will (a Christian concept)