Two comments
1. That chart has another large error, it leaves out the very large contribution made by Islamic (Arabic) scholars up to say the end of the 12th or 13th centuries. It seems that, not only did scholars of that era rescue previous Greek scholarship (which had often built on ancient Egyptian science and medicine) but they led subsequent scientific progress. Toby Huff writes in his well-regarded, ' The Rise of early Modern Science - Islam, China and the West,' (Cambridge University Press-2003). (You can find a -limited page- copy on google books):
Quote from p.48
"... from the eighth century to the 14th century, Arabic science was probably the most advanced science in the world, surpassing the West and China. In virtually every field of endeavour - in astronomy, alchemy, mathematics, medicine and optics ... Arabic (i.e. using the Arabic language, but possibly Iranian or even Jewish) scientists were in the forefront."
2. My second point is that it is not true that Christianity was not present in China in both the early and medieval era's. The Church of the East, also called the Nestorians, are definitely attested in China as early as the seventh century, (Tang dynasty) and were given permission to build monastries in a number of provinces. They disappeared during the clampdown on foreign religions (which included Buddhism) aprrox. two hundred years later. They were again present in China during the (Mongolian) Yuan dynasty but were seen as too close to the Mongols and were again expelled. During the Yuan dynasty there were also representives of the Catholic church in both north and south China, one at least has written of the generosity of the Imperial administration toward them, and then again in the Sixteenth century, the Jesuits gained permission to have a mission in Beijing, and down in the south in Fujian and Guangdong the Dominicans infiltrated from the Phillipines which the Spanish had annexed. Conflict between the two orders, again brought government bans.
It is quite clear that the opportunity for mass conversion was there, but did not happen. Why? I suggest that Christianity just did NOT appeal to the Chinese mindset based on Confucianism and Daoism. Buddhism became accepted because Buddhists were prepared to adjust their concepts to the patterns of Chinese thought. It is also true, that China changed Buddhism and a profusion of new schools of Buddhism arose, of which Chan (which the Japanese also adopted and called it Zen) has become the most well-known.
