Hello soulcalm17

[Paleophyte]

Thanks all for the details of what I informed. But let me complete what I knew of Hinduism.
That is correct that Upanishad and Bhagavad Gita came later than old Vedas. But if we read the detail of Vedas, it still point to the monotheism instead of pantheism.
Rigveda, is the oldest of all type of Vedas.
The Rigveda states in book I, hymn 164, verse 46:
Sages (learned Priest) call one God by many names.
(This is states that only one God, but have many names)
Brahma (means The Creator) as well as Visnu (means The Sustainer), indeed the name of God mentioned in Rigveda book II, hymn 1, verse 3
What support my statement that Hindu is actually monotheism by its scripture is mentioned in Rigveda book VIII, hymn 1, verse 1:
O, friends, do not worship anybody but Him, the Divine One. Praise Him alone

And in Yajurveda, there is the verse that's same with the content in Upanishad. Here it is:
1. There is no image of Him (Yajurveda 32:3)
2. They sink deeper in darkness, those who worship sambuthi (Yajurveda 40:9)
*Sambuthi means created things, like table, chair, idol, etc

So I still conclude that in Hindu, monotheism changed to the pantheism by it's followers.

The problem is, might be the researchers only observed on the practicing of the religion, not observing the scriptures itself.

It is actually the case of all religion I suppose. Later on insha Allah I will give evidence that many religions rooted in monotheism.

Using scripture as a guide to history is always perilous. It assumes that the original was accurate and that your translation isn't flawed. In this case I'd suggest that you're also doing a lot of cherry picking. You have a few select verses here that you've quoted without context, whereas the overwhelming bulk of Hindu scripture is clearly polytheistic. The archaeological record also shows that the Hindu cultures have always been polytheistic. In any culture as rich as the Hindu pantheon you're bound to get some henotheism arising locally, but I think that's about as far as you can take it. The overwhelming bulk of the evidence simply doesn't support your case.