Prior to Sage Sankara in the 8th century, there was no Advaita in Santana Dharma.+

Prior to Sage Sankara in the 8th century, there was no Advaita in Santana Dharma. Santana Dharma or Vedic religion has no founders whereas Advaita and qualified Advaita and Dwaita are identified with their founders. All of them have non-Vedic rituals barred by the Vedas.

The dualism came only in the 12th century. The orthodox Advaita and Dwaita area adulterated add-ons. Both Advaita and Dvaita schools claim that they are based on the Vedas and they condemn each other with the Upanishads and Puranic citations and try to prove they are right and others are wrong.

The religion, including orthodox Advaita, has nothing to do with the ultimate truth or Brahman because they worship idols, human worship, and symbol worship and indulge in non-Vedic rituals barred by the Vedas.  

Remember:~

Most of the Indian Saints and Gurus of the past founded different sects castes and cults and sects with their own beliefs, Gods and Goddesses, codes of conduct, traditions, and culture in different regions of India.

Most of the Saints and Gurus of the past are mostly social reformers, thus, they are more concerned with humanism rather than the truth. Their contribution is very valuable to humanity. Thus, humanism is limited to practical life within the practical world.

The path of love is the path for humanity; therefore, it is the individualized path. Thus, the path of love is limited to the physical structure; it cannot transport one to the ultimate end. Thus, the seeker has to understand the fact that, from the ultimate standpoint the practical life within the practical world is merely an illusion created out of the Soul, which is present in the form of consciousness. Thus, love, hate, and the world, in which you exist, cease to exist as a reality in self-awareness.

The simple reason is that the average person may have a desire for knowledge, but when the whole society is immersed in the belief system and feeling himself out of place because of societal fear and surrounding circumstances he thinks, it unfits him, to pursue the path of truth. :~Santthosh Kumaar