Buddhism not only spread in India with great intensity but also spread in many countries of the world. Buddhism spread to countries like Sri Lanka, Japan, Java, Sumatra etc. Since the time of Mahatma Buddha, Buddhism has been steadily propagated and its propagation had reasons for religious, social, economic and kings, the details of which can be seen below.
Social reasons - The post-Vedic period was a period of decline from the point of view of society where on the one hand the varna system (Brahmins, Kshatriyas, Vaishyas, Shudras) emerged in the society due to which there was a decline in the status of the Shudras and untouchability, untouchability towards the Shudras in the society. The practices included the Shudras did not have the right to education, Upanayana, and the right to Yagyas.
Apart from these circumstances, the condition of women declined in the later Vedic period. Now women do not have the right to education, upanayana, to see women
In all the Brahmin texts citing the reason women were condemned, Buddhism became popular among these circumstances as a result of the upliftment of women.
Economic Causes - As a result of the Varna system in the post-Vedic period, the economic situation has declined, the people of the higher clans are in the opposite position.
They could adopt the profession of lower caste than themselves, but the lower caste people could not do it under any circumstances, in the meantime Buddhism developed, due to these economic reasons, people were inclined towards this religion.