The Gorthect empire
The eastern continent was larger than the middle continent, both in size and human population.
Both the continents didn't have much difference when looked solely at the size.
There were many reasons why the eastern continent had more human resources compared to the middle continent.
The main reason was that, nearly half of the middle continent was nothing but desert. Leading to the difference of land available to the three ruling forces to take over.
The difference in technology also played a role. Being prosperous in alchemist enabled the people of the eastern continent to have a better environment to give birth and live. But in the other hand there were tons of rules banning murder, robbery and other crimes. This would get in Zick's way without a doubt.
There was also an order which maintained the said rules. But their was no such thing as human right as of yet, after all slavery and prostitution was a normal thing in this continent.