Sons of God!

"..when the 'sons of God' saw the 'daughter's of men' that they were fair, they took them wife's, of all they chose... Gen. 6:2 "

" offspring were giants. Gen 6:4 "

Giants yes, but perhaps not as big as the one depicted!
The Bible depict's many encounter's with aliens or their offspring, only the alien's were thought of as 'god's', and their offspring as 'mighty men of old'.
Advanced technology, being able to fly through the air, the 'fire' show's, etc. were pretty convincing to a primitive people.

Meanwhile, the other side of the world, was seeing blue men, who had another set of arms,(see the side panel) and elephant like snout.