History says India was a land of saints [Rishis] but in the course of time it became a land of temples. Undoubtedly we can say this transition marked the beginning of philosophical and cultural degradation of India. Early India had no concept of temples they worshipped Agni, Indra etc just like Persians who considered Fire as the supreme.
Reasons that learned cite for the origin of Hindu Temples:
a) Puranic Hinduism required a location where the deity could be established permanently in an appropriate building for worship. Even though the worship was devotional and awaited the grace of the deity, an icon could be the focus for devotion and the giving of gifts.
An icon was not necessary but gradually became common. The centrality of the icon further distanced purnaic Hinduism from the Vedic religion.[338 wonder that was India]
b) Basic rites of Vedic religion were sacrifice that of Hinduism is worship. The temple originated as a small wooden but enshrining a rough icon or fetish. Temples played no part in Vedic religion and none has been traced in archaeological sites from before the Christian era. It is possible that they were introduced as a result of the wave of foreign influence following Greek and saka invasions. [338 wonder that was India]
c) Vivekananda says Buddhists were the first to use Images/symbols which was unknown before then. Which means until 6th BC India never depicted any form of Human God. Buddha was the first human God if we can say so.
"By and by, there arose huge temples and all the paraphernalia. The use of images was unknown before then. I say they were the first to use images.There are images of Buddha and all the saints, sitting about and praying. ~Swami Vivekananda"d) Indologist Bhasham makes Close observation between Hindu temples and Greek temples. Greeks had built temples much before Indians which suggests Hindu temples were inspired by Greeks. [ Source]
e) Also as a part of Revival of Vedic Hinduism which had taken a back seat with spread of Buddhism, likes of Shankaracharya built Mutts which were nothing but counter part of Buddhist Monastries [ Source]
Agni, Indra and varuna were the chief Gods during the vedic age and were frequently invoked with Vedic Mantras who fulfilled the wishes of Vedic priests irrespective of the sanctity, moral degree of the Man who carried out the ritual under the supervision of the priest. Commit a Sin recite the Vedic Mantra, Commit a Sin dip in Ganga get rid of the sins that you committed. This was the central philosophy of puranic Hinduism, hence it extensively propagated offerings and donations and made it almost mandatory for common men and thus became financial centres. [ S1 , S 2]
But Upanishads which condemned these silly Vedic rituals and the Emergence of Light of Asia "Buddha” gave way to new religions and theories which were well embraced by the common people who were not able to bear the costly Vedic rituals. Post Buddha as discussed above Human Gods like Rama, Krishna etc arose who virtually finished the Vedic Gods and became the Supreme Gods and bag full of stories were written to support them.
Thus for historical reasons Indra and agni and Surya were ditched and Puranic Hinduism a brain child of the priest craft a lower version which is must and necessary to comprehend the higher philosophy as claimed by priests in comparison to Upanishad Hinduism ditched Agni,Indra and surya introduced Human Gods like Rama, Krishna etc.Citations:-
Vivekananda: Origin of Temple | Vivekananda condemns priests for making temples trade centre |Romila thapar: Temple - commerce- priests
Hindu Temples influenced by Greeks | Earliest Religious building
No Recitation of Vedic literature in temples | Temples and Maithuna Figures
Gandhi Condemns priests | Devadasi are the priestly gift to Hindu culture
Temples Even Today are spreading Inequality among fellow human beings, a black mark on my nationInequality practiced in Dakshina Kannada temples Even Today |Vibrant Gujarat a Myth, 1655 villages practice Inequality source tracked to temple
TN Priests happy allowing discrimination | Even now untouchability rampant in Orissa temples
COW SHIT PURIFIES WHAT A HUMAN BEING MADE UNCLEAN