There was an earlier comment answering this that had many inaccuracies in it. I wrote up a reply to it but it has since been deleted. I'm posting my reply anyway in an answer to OP's question:

Unfortunately, there are a number of inaccurate statements here that should be corrected

To first answer this question it should be noted that the modern version of the poem was believed to have been derived from an ancient Scandinavian fable; however, this cannot be definitely proven as it believed that the original fable was passed down through oral tradition.

It doesn’t really make sense to speak of a “modern version” of the poem. There is only one version of the poem, copied by two scribes in a manuscript (known as Cotton Vitellius A.XV) around the first decade of the eleventh century, alongside several other poetic and prose texts. We do not know where the origins of the stories come from. It contains actual historical persons (Beowulf’s king Hygelac, who died around 516 in a raid on the Franks according to Gregory of Tours. It contains “monsters” similar to those found in other, much later Scandinavian stories (like Glam in Grettis Saga and the dragon-like monster killed by Boðvar Bjarki in Hrolfs Saga Kraka), and semi-legendary figures like Hrolf Kraki himself (Hroðgar’s nephew Hroðulf in Beowulf). To say that this comes from an “ancient Scandinavian fable” is far too simple a notion to explain origin of the story. It should be emphasized that the Icelandic Sagas that have similar narratives are all much later than the poem.

The first manuscript of Beowulf was produced in England during the 7th century, a period when Scandinavian settlers and raids were becoming more commonplace.

As for the date of the poem, as I said above, the manuscript is from around the first decade of the eleventh century. This date is based on the handwriting of the two scribes, since there are no other dating criteria found to narrow it down. The date of the poem entirely unknown and has been argued about for well over 100 years now. Dates from the seventh century to the reign of King Cnut (1016-35) have been proposed. As for the Scandinavian raids, it is unclear if by this you mean original Scandinavian settlers of Britain from the post-Roman period (i.e., those who came in with the arrival more often associated with the Angles, Saxons, and Jutes), or the Vikings, whose first raid in England was in the late eighth century (793) on the island of Lindisfarne.

Whatever the connection, many have sought to connect the origin of the poem with Scandinavian settlers/invaders as a way to explain why the poem takes place in Scandinavia with characters well known in later Scandinavian history, but the chief obstacle in doing this successfully is that the poem was written so much earlier than most of the Scandinavian sources. Perhaps the most basic level of connection is simply that the Anglo-Saxons were Germanic and thus their folktales would reflect Germanic tradition in the same way that Scandinavian folktales (and those in Old High German also) would. So there is a natural Germanic connection between Old English poems like Beowulf, Widsith, The Finnsburg Fragment, Waldere with the Scandinavian stories already mentioned, as well as others like the Volsung Saga, and also with Old High German poems like Hildebrandslied and the Medieval Latin poem Waltharius (telling a story similar to Waldere). Others have sought to make the connection much more specific, seeing the poem as a glorification of the Scyldings (Skjoldungs), who were promoted (if I remember right) as ancestors of the leaders of the Great Viking Army that invaded England in 865. The later tenth-century Viking invaders Harold Bluetooth, Sweyn Forkbeard and Cnut seem to have tried to connect their family to these earlier invaders. That could suggest that the poem derives from descendants of Vikings who settled in the Danelaw after making “peace” with Alfred. This is the time that the Old Icelandic term þjóðkonungr “people-kings” starts appearing in tenth-century Scaldic poetry, often written in England, and is the equivalent of ðeodcyning found in line 2 of Beowulf. That word was increasingly used by the family of Cnut. On the other hand, since Beowulf is earlier than these other stories, it may be that the influence was England > Scandinavia via the settlers rather than the other way around. The actual answer to this question remains one of the central points of controversy in scholarship on the poem.

Upon its initial translation, and multiple transcriptions, the story slowly began to adopt subtle Christian themes and motifs. For example, Grendel and the dragon are referred to as enemies of a Christian God, unlike the monsters typically described in traditional Scandinavian lore. Another example would include the multiple parallels that exist between Beowulf and Jesus, as demonstrated by countless literary scholars. The themes, motifs, and ideologies presented in the poem essentially fuse the ideals of Scandinavian courage and honor with the Christian faith and outlook.

The last sentence here is a good summary of current thinking on the interplay between Christianity and paganism in the poem. But the first sentences aren’t. There is no suggestion in the poem anywhere that the poem was ever a “translation” and we have no idea how many “transcriptions” the poem went through before being copied into Vitellius A.XV. Nor is there any evidence that the poem moved from an essentially pagan story to a Christian one (such thinking was common in 19th century scholarship when people would try to remove Christian elements of the poem to restore it to its original pagan form). The poem as we have it reads as a poem written by a thoroughly Christian poet for a thoroughly Christian audience about pagan Germanic ancestors who in spite of their paganism did the best they could against forces of evil, even though they may have not understood the origins of that evil. The poet speaks of Grendel as an enemy of God and a descendant of Cain, but the characters in the poem do not. Beowulf, although pagan, is a virtuous pagan, fighting against evil, but the poet does point out early on that pagans do the work of the devil, and that the Danes prayed to idols and cast lots and as all pagans would end up in Hell after death.

Literary scholars have provided several theories that attempt to disclose the meaning behind the poem. The predominant theory states that, given the historical context, the poem was utilized to help encourage Scandinavian people settling or raiding in England to convert to Christianity.

The scholarly work I have read would say the opposite. The poem would be terrible as a way to convert anyone to Christianity. It contains nothing about the story of Jesus, the incarnation, the resurrection, the redemption of sins, or any other point of essential Christian theology. The only thing we have in the poem is a very vague description of the creation of the world that at least does not contradict Genesis, and statements about Grendel and his mother’s descent from Cain. References to God are kept vague as “the almighty one” or “the father” and when spoken by characters in the poem could refer to Woden as equally as to the Christian God. There is also nothing to help encourage settlement, since the poem is located entirely in Scandinavia. But as you say there are many theories about the poem, its meanings, themes etc.

Edit: Sources: Information found in the post is readily available in the Old English editions of Beowulf. The 4th edition of Klaeber would be the place to go. I would also suggest Orchard's A Critical Companion to Beowulf. On the dating of the poem, the collection of articles in The Dating of Beowulf, ed. Chace is still good (it contains the information on the connections between Beowulf and Skaldic poetry mentioned above). Newton's The Origin of Beowulf has a lot on the possible connections between Beowulf and East Anglia and Scandinavia.