I believe a dev confirmed that the lore of the Maw was that it originally was only Torghast, and Zovaal used chains to drag the rest of the landmass in. Hence why he also drags Korthia into the Maw.
https://wow.gamepedia.com/MawThe landmass within the Maw consists of pieces of land that have been ripped from a realm that was destroyed upon entering the Maw's atmosphere and whose pieces have become burned and desiccated. The Jailer pieced these together into a single landmass by throwing out chains in every direction within the Maw from Torghast and pulling them inwards.[13] The Maw was sealed and made inescapable with the magic of the Heart of the Forest, with the goal of banishing The Jailer forever.[14]