A documentary made by the Chinese government eulogises its ancient imperial glory and the spirit of unification. Nothing but a propaganda! Those counties with 'glorious' imperial history: Russia, China, Turkey, Iran, need to be de-imperialised fully so as to be truly modernised countries.
Not pursue unification, but the Kings or emperors pursue power and wealth and glory with having an ever more bigger area under their governance. I have seen that in almost every nation history on earth, be it China, Korean, Japan, ancient Java / Indonesia, Egypt, Babylonia, Persia, Mongolia, Burma (vs weaker Thailand), Ottoman of Turkey, Abbesinian dinasty in Middle East etc etc etc
Actually land grabbing is not attractive before colonization period. The reason is that logistic wasn't developed, trading is a small part of economy. A small economy may expand due to its lack of resources. Large economy normally tend to stay stable.
While it’s true that most kings do pursue power and wealth this was not main driving force in this period in Chinese history. These kings are more like Barons that serve under the Zhou emperor (the son of heaven). The emperor initially gave lands around the emperor’s domain to these barons to create buffer states. Overtime these barons expanded their territory outwards and soon even welded more power and wealth than the emperor. Even though the emperor was now just a ceremonial figure head, the position of “son of heaven” was so prestigious that all of them fought for it.
What a pity you are. We can still understand our ancester's articles written thousands years ago. Chinese culture and languange have continued thousands years without disruptions. I am so proud of my ethnic chinese though I live abroad.