According to Guns, Germs, and Steel, why was China able to dominate east asia?

China was not originally monolithic. China was populated
by people who spoke a large variety of languages that were separated by historians into
four groups: Sino-Tibetan, Austroasiatic, Tai-Kadai, and Miao-Yao. Sino-Tibetan consists
of the eight main languages in China today: Mandarin, and seven of its close relatives.
It is speculated that Sino-Tibetan originated in North China, and Austroasiatic,
Tai-Kadai, and Miao-Yao were the native languages in South China. Sino-Tibetan spread
into South China when a writing system was created by North China, and was spread using
canals connecting the Yangtze and Yellow rivers. The first three dynasties in China were
mainly in the north, and not until the Qin Dynasty in 221 BC did China unify. Prior to
this point in history, many North Chinese considered South Chinese people to be
barbaric. China was able to dominate East Asia with their strong Dynasties and
languages. Language spread unified China when Mandarin was developed and spread
throughout the country. North China was also able to dominate East Asia with their
advanced innovations and technology.