Lemuria first began to become a scattered wasteland after its depositories initially became chemically unstable. Many cataclysms were brought on including the first nuclear winter, ever..
The people were separated into warring factions who were all vying for the best land outside of the Lemurian Kingdom. This would form a ring of Urbanization called Ur, surrounding the vast Empire from which the Hyperborian’s ruled the entire world. They were able to reform their old world control, but at the expense of an elite federation of giants who had to guard their vast homeland from invasions. Their descendants became the Philistines, who would end up assimilating with the general population after the time of their original progenitors would pass. They gave Goliath to the Hebrew Philistines who had began to heavily populate the entire world during these final days of the Hyperborians.
The Kingdom of Bashan was the last Stronghold to be held by the Hyperborians and the land was reported to be still copiously green and flowing with milk and honey.
A power vacuum was created from within the heart of Bashan, and it became occupied by the giant warlords and heroes of the days of Noah. They effectively ran the vast post-flood megalopolis, for a little while, before it was to break down and disintegrate into the empires of Babylon, Egypt, Assyria and Hatti.