Swallowing the Swamp
Turning back the clock a bit...
The swamps that Zhen Liu and his cohort were traversing weren't normal swamplands, rather, they were at the very edge of the lands known as the Endless Swamplands.
Due to the Endless Swamplands' location, the region was basically bordering neighbors to every single nation and kingdom that called Roaring Tide home. Literally, the only way to get from one nation to the next was through the Endless Swamplands, at least if one was going through internal routes as opposed to coastal travel.
The Endless Swamplands were, essentially, the equivalent to a certain blue planet's Silk Road, but significantly more moist and wild.
In other words, if a nation, sect or top tier cultivator were to claim the Endless Swamplands as their territory, they would become the penultimate hegemon on the continent.
However, there were two major reasons as to why this hasn't occurred yet.