What was the main reason Buddhism spread from China to Korea and Japan?

The main reason Buddhism spread from China to Korea and Japan was through diplomatic missions, trade, and the activities of Buddhist monks. It was not because of invasions or military conquests. During the Tang dynasty, Chinese monks traveled to Korea and Japan, bringing with them Buddhist texts, rituals, and practices. Korean monks also made pilgrimages to Tang China to study Buddhism and returned to their home country to spread the religion. Similarly, Japanese missions were sent to China to learn about Buddhism, resulting in the introduction of the religion in Japan. Cultural exchanges and intellectual discussions between Chinese, Korean, and Japanese scholars and monks contributed to the diffusion of Buddhism across the region.