They needed to have enough supply for food is what I would say because if you don't eat you will eventually get weak and die.
Hope It Helped :D
They could not govern every part of the country at once as the word of a new law for example would take months to get from one place to another Ik this is just one sorry
It happened because the market was oberbought
The dynasty that restored unity to China after Shi Huangdi's government crumbled was the Zhou Dynasty