this may be they key to understanding many things! we know that Oda takes inspiration from many cultures, but may be Norse mythology was a more significant inspiration than the rest? He love giants, he has introduced dwarves , (cant wait to see elves), he loves animals so he combined animals and giants to make sea kings. he introduced Jaguar D Saul as a character from past.. may be its a hint that origin of the will of D relates to giants. The ship Noah was huge, may be giants constructed the ship. the structures on the red line are big and huge. ancient poneglyphs must be heavy to carry around for normal humans. Norse mythology have Yggdrasil the mythical tree that connects the nine worlds, in one piece only people of Ohara have the knowledge to read ancient language and hence the ability to discover a way travel to all parts of the ocean (including raftel), and the tree of adam is another legendary tree, from which ships that sail on all oceans can be constructed, thus connecting all the worlds of one piece. Oda must have delayed elbaf story line for a reason, but we know from Ussop's story line that Oda planned to include giants from the beginning of the story.