Although more of an idea then a full theory, I thought this was interesting to bring up. The idea of BotW being on the downfall timeline and explaining the rock salt we find. This map I found on ZU, a bit messy, it shows how the locations of AoL fit on BotW's map. The idea would explain why we find rock salt "from an ancient sea" The planet grew hotter thus raising the ocean levels. Then after those tens of thousands of years between AoL and BotW the water levels receded. Spectacle rock, and the King's tomb also line up nicely, as well as the swamp. This also reminds one of the map done that showed ALttP's map compared to BotW. So in the time between ALttP and AoL Hyrule must have flooded due to climate change.