Because are strong and can fight for their right.
Answer:
The basic doctrines of early Buddhism, which remain common to all Buddhism, include the four noble truths: existence is suffering (dukhka); suffering has a cause, namely craving and attachment (trishna); there is a cessation of suffering, which is nirvana; and there is a path to the cessation of suffering, the eightfold path of right views, right resolve, right speech, right action, right livelihood, right effort, right mindfulness, and right concentration. Buddhism characteristically describes reality in terms of process and relation rather than entity or substance.
The silk road stretched 4000 miles from China to the Mediterranean Sea and was linked to the Mediterranean countries by ports and ships. It included China, India, Persia and Arabia and allowed for two-way trade of such things as silk from China and woolen goods such as carpets, curtains, blankets and rugs came from the western countries along the route, for example.