Since Hinduism reinforces the caste system and Buddhism believe in equal treatment of all people which opposes the caste system, Buddhism started to spread into other areas other than India to offer an alternative to Hinduism for those in a lower caste. As Buddhism started to diffuse into other regions, the popularity of Buddhism in India started to decline because Hinduism gradually displaced them and became the more popular religion in India. Hinduism beliefs still continue to influence Indian society today. This changed more likely occurred because Buddhism would not have been as compatible with Indian culture in India as Hinduism has a more stronger tie to Indian culture like the reinforced caste system.
The spread of Buddhism through 600 CE was diffused among other countries. Buddhism started out in India and rapidly grew throughout the world eventually traveling along the Silk Road and spreading to areas like China, Korea, and Japan. While Buddhism was spreading in other countries, Hinduism tended to stay mostly in India. Because Hinduism was more complex, it made Buddhism more easier to comprehend and understand because they accepted everyone equally while Hinduism weren't accepting of people not born into the caste system. This change more likely occurred because Buddhism and Hinduism have slightly different views on the equality of people which benefited Buddhism to diffuse their religion in other areas besides India.