Distorted forms of Gods: In Vedic age, the Aryans worshipped the different powers of nature, gods etc. They used to consider them as their friends. In due course of time this concept changed and god was considered to be absolute, willful and controller of all the acts and action of human being. Thus the position of man became very low and humble before the god. It, therefore, became necessary for the religious reformers to aim reforms by having sympathy with man.
Religious Rigidity: The simplicity of the religion in Vedic age had become a thing of past. Religion had become very rigid. There were innumerable gods and goddesses and their worship had become showy and complicated, a reform was, therefore expedient to remedy this situation.
Burden of Ritualism: There were very elaborate and expensive rites and rituals had taken place of simplicity and purity of religion and philosophy of the Vedic age. Sometimes sixteen, or seventeen purohits were required for performance of a yajana which was not within the means of a common man. Sudras were completely prohibited from the study of Vedic literature and the performance of yajana. These were the reasons that created a sense of spiritual unrest and dissatisfaction among the people in the society.
Social evils: One of the main reasons of the religious revolution was the social evil, which had crept in the society due to deterioration of the caste system. This eventually had become hereditary. Brahmanas were exploiting the other castes and particularly the Sudras who were denied all rights and were treated very badly. Superstitions and other evils were increasing in the society. There was a widespread discontentment among the people as well.
Ethical degradation of Brahmanas: Degradation of brahmanas was one of the main causes of religious revolution. Brahmanas were now leading a life of comforts and luxury. They were becoming more and more materialistic. Their moral and ethical degradation had created discontent among the people.