The spread of buddhist ideas and customs to china and southeast asia was the result of

Buddhism is China's oldest foreign religion. It merged with native Taoism and folk religion. Ancient Hindu Buddhism taught by Buddha involved reaching Enlightenment through meditation. How to go about this and what it means is open to interpretation. When early Buddhist scriptures were translated into Chinese, Taoist terminology based on native religion was often used. People interpreted the scripture in their own ways. 

Buddhism has had a long history in China, and native Buddhist religions developed that are accepted by Chinese Buddhists.