It is certainly true that Satan has done his best to sew false and confusing myths throughout history to minimize and hide the truth. Like flares and chaff to distract missiles from finding the real aircraft.
But Christians have Jesus Christ in person, spending years with ordinary but highly credible people who in turn spent decades sharing their experiences with startup churches all around the Mediterranean Sea.
This is the basis of Christianity and the primary reason why people believe the narrative about Him. Not vague story telling around campfires over the preceding millennia.
Jesus specifically stated that the Hebrew Scriptures (a.k.a. "Moses and the Prophets") were true and should be believed: "If you believed Moses, you would believe me, for he wrote about me. But since you do not believe what he wrote, how are you going to believe what I say?"
So our faith has solid grounding in real people at a real place and time and is not derived from other ancient myths.
Assuming that the myths described in this video are not the products of the authors imagination stated in a way to maximize the correlation with Jesus' story, I can think of a combination of several ways they may have occurred.
- Christian history / Jewish prophecy goes back to around 4000 BC so there is lots of opportunity for information to flow the other way - from them to other surrounding cultures.
- Satan is actively engaged in planting false rabbit trails everywhere he can. Jesus said he was "the father of lies".
- Pagan stories did get mixed in with Christianity by the misguided Roman church over the centuries. They happily added the pagan "Christmas Tree" and moved the celebration of Jesus birth to December 25th to make it more acceptable to Pagans (and to Preempt their existing holidays with Christian alternatives.) This so-called "Christian" activity was also the work of Satan, sewing more confusion and lies to obscure the Truth.
So I stay grounded in specific eyewitness accounts of what Jesus did and said and what his followers learned from Him - in person and through his promised guidance by the Holy Spirit.
It is a fascinating video however. It just gets its causes and effects mixed up.