The century or so before Islam has been termed the “Buddhist Age.” Buddhism had taken root in China as an indigenous and vital religion, and began its spread to Korea and Japan. Hindu and Buddhist influences were also evident in Southeast Asia. Men of Indian origin such as Kumārajīva were prominent at the time in China, teaching the tenets of the new religion and translating its scriptures into the local language. Though the figures at the courts of the kings of Angkor and Srivijaya are more vague, it seems implausible that Indian culture could spread without some Indian individuals. In the domain of “hard power,” the peninsular Cholas of the Tamil lands at their peak claimed hegemony over much of maritime Southeast Asia.
What happened? I think without getting into too controversial a territory native Indian cultural traditions clearly took a defensive crouch after the hammer-blow of the Muslim Turk raids, and then later the Islamic hegemony across much of South Asia. Unlike the Zoroastrians of Iran, or the Christians of the Near East, South Asians maintained their indigenous religious traditions by and large. But like Rabbinical Judaism, Indian civilization was transmuted by the thousand year awkward condominium between Islam and the Dharmic traditions. I must admit I find it ironic that some of the most anti-Muslim Indians I’ve met are also the most obviously attached to the involuted and exclusive forms and ways of Hindu civilization as it developed by necessity when faced with a religiously alienated ruling class.