how did buddhism became popular in India as compared to jainism????????

Due to many reasons, Buddhism gained more popularity than Jainism. Although both the religions were founded as a rebel against the strict, conservative nature of the Brahmanic traditions, one gained more popularity than the other due to these reasons.

1. Jainism preached very strict vegetarianism and non-violence. The customs and beliefs are very strict as against some sects of Buddhism which do not stress on vegetarianism.
2. Buddhism gained patronage from some very strong emperors like Ashoka, who even sent missionaries to other countries to propogate the religion. He adopted many steps like erecting pillar and rock edicts to popularise the religion.
3. Jainism was limited to specific regions like Marwar, Gujarat and parts of South India while Buddhism gained popularity throughout the country including the Himalayan regions.
4. Buddhism appealed to many foreign cultures like people in Sri Lanka, Tibet, China, Japan, Burma and Thailand.