The biggest contribution of Bharatiya Vaidika Arya Hindu Culture to the entire world in terms of Upasana is the Tantrika concept of 'Devo bhootva devam yajet', which has inspired Sufis Christianity etc. The concept is present in code form in the Vedas but expanded thru Tantras. +

Modern historians and indologists includi hindu ones like to attribute diff type of evolution in the shaastras, some of it is true, sm of it is enforced. Before understanding this uniqje and revolutionary concept, rmv d mindset that Yoga Upasana etc came into Vedas thru Tantra.

Also ppl lIke Winternitz confined the word Tantra only to the Shalta school, which also is a huge blunder and the modern understanding of this word has become limited to magicstuff. Which also isn't true. So by tantra i mean the Aagamas, vaishnava shaiva shakta Saura skaanda etc.

Coming to the concept, 'devo bhutva devam yajet' means 'worship the deva by yourself becoming a deva'. This can be seen why Vaishnavas first cleanse and purify themselves, they invoke the dvinity in self first. Then also add 12 tilakas on 12 places. +

Just like Vishnu, they wear the shankha chakra also. Only a divine being can worship ajd establish union with the divinity. This is a very advanced understanding what most indologists and academicians fail to shed light upon, they're only focused on enforcing liberalism. +