[riazrizvi]

Clearly by the 13th Century China could be considered a technological forerunner, but then the Mongols took over. I suspect the cultural tendencies of the Chinese civil service that drove innovation just couldn’t weather the merging of cultures and the scholarly edge of Chinese culture was collateral damage.

[dredmorbius]

I'm still very weak on my Chinese history, but it was the turning-inward of the Ming dynasty (15th century), not the Mongol invasions, which precipitated the halt.

Also (as already mentioned in this thread), the asset-sheltering tendency of established power groups, halting the emergence of potential rivals, as Bernhard Stern documents in other (non-Chinese) instances.