Option 1 says Buddhism was in the ascendant at that time, implying that Buddhism was popular and influential during that period. However, the popularity of a religion alone would not necessarily make foreigners embrace it.

Option 2 suggests that Greeks, Kushanas and Shakas chose Buddhism because they had renounced the policy of war and violence. Even though Buddhism preaches peace and non-violence, it doesn`t necessarily mean that this was the sole reason these groups adopted Buddhism.

Option 3 suggests that caste-ridden Hinduism did not attract them. But the existence of caste in a religion might not be a key deterrent for someone from another culture or religion to embrace it as long as its principles align with their beliefs.

Option 4, the correct answer, states that Buddhism offered easier access to Indian society. This is plausible because Buddhism, unlike Hinduism, did not have the rigid caste restrictions and hence was more open to foreigners. It was easier to integrate into Indian society through Buddhism. Therefore, many Greeks, Kushanas and Shakas embraced Buddhism rather than Hinduism.