Your conclusions are rather questionable. Before the advent of Islam in Northern India, Shaiva siddhanta was the sect that received royal patronage in 10th & 11th centuries. The Hindu Shahis of Punjab were of Shaiva predisposition. Lakshmidhara, a courtier of the Gahadavala king Govindachandra of Kannauj, cites a Shaiva agama called Kalottara while compiling a list of festivals in his Krtyakalpataru. The Pala rulers of Mithila+Bengal & the Bhaumakaras of Odisha had also turned away from Vajrayana to Shaiva siddhanta at this time.

Eben as far as in South, the Chola were devout supporters of Shaiva siddhanta. Rajendra Chola is said to have imported Shaiva siddhantavadi brahmins from Bengal after his Gangasagar campaign. The advent of Islam completely changed the inter-denominational demographics if Hinduism. Without royal support, Shaiva siddhanta died out in North India & was supplanted by Vaishnavism (at the behest of Ramananda). In South Srivaishnavism arose on the support of the Hoysalas & Madhvas through the Tuluva dynasty of Vijayanagara.

Throughout these turbulent times, Puranas have undergone significant modifications at the hands of zealots. I once found a passage in Garuda Purana praising Madhva. And at the same time, there are passages in the Saura Purana describing Shivadveshi Madhva sannyasis & allegations of them indulging in sex with low-caste women as signs of Kaliyuga. Hence the study of history is necessary while studying religious history.

Just look around, TODAY. The only sectarianism that has ANY significant following today is Vishnuism in its several flavors @অনু . Royal patronage obviously had its ups and downs in history, but you can see that the sectarianism of TODAY's Vishnuists is hardly different from what it was in the medieval period.

Belonging to a sect doesn't means automatically being sectarian. In my native place of Bengal, although most of the middle & lower castes profess Gaudiya Vaishnavism as professed by the local Goswamis, but they aren't averse to worship of Adyashakti (unless being extremely bigoted), whereas ISKCON treats the worship of other avatars of Vishnu as heresy & other deities as blasphemy.

Similarly Ramanandi dominated North India also fervently observes Shivaratri & Navaratri. And pre-Islamic medieval Vaishnavism is somewhat different from its modern version. I have a copy of a rare Hayasirshapancharatra manuscript currently located in Paris, which describes consecration icons of archaic Vaishnava forms like Vaikutha Chaturmurti, Vishwarupa & 14-armed Ananta alongside Bhairava, Durga, Matrikas, Harihara, Ganesha, navagrahas & shivalingas. Pancharatra texts like Sanatkumarasamhita & Padmasamhita also discuss the worship of Durga, Shiva, Ganesha, Kartikeya & Surya.

But present day Pancharatrikas don't worship these deities at all, following in the footsteps of Ramanuja. And in this impermanent world, everything is temporary, including the rise & fall of sects, so you shouldn't be much concerned about it.

i think these "my God can beat up your God" arguments are childish - but it seems to be a live issue TODAY only to Vishnuists. I am looking for a factual answer if my perception is true. @অনু

Speaking of today, it is very unlikely that the sort of bigotry you are referring to is mainstream even amongst Vaishnavas (barring ISKCON, whose founder had sweet words for Muslims & Christians but none for non-Vaishnava Hindus, as seen in Vanipedia), due to external pressures (read proselytization from other religions & advent of atheism). And your viwe that the religion has been quote-unquote 'Vaishnavised' is untrue, as proved by my previous arguments.

Scholars use textual analysis to claim that Rama was not an inacrnation of Vishnu in the early versions of the epic. Suktankar says mahabharata was similarly Vaishnavized by Bhargava poets. please see "historical evolution of the Ram legend" by Suvira Jaiswal . @অনু In fact, Goldman says Ramayana can be considered the foundational text of the Srivaishnavite sect.

"Suktankar says mahabharata was similarly Vaishnavized by Bhargava poets." - Source please.

@অনু Very detailed response (খুব বিস্তারিত এবং ভাল উত্তর). You should write that as an answer in my humble opinion.

"The Ramayana is a story of Vishnu killing a devotee of Brahma/Siva" - where does valmiki ramayana or vyasa mahabharata address ravan as "devotee" of brahma/rudra ? Or for that matter does vishnu puran or bhagvata purANa address ravan as "devotee" anywhere? I guess only vernacular ramayans, tv shows etc make him. "devotee" of shiva.

@estimator take a look at benjaminindology.wordpress.com/2020/08/30/… the benedictory "narayanam namaskritya" verse is also considered an interpolation by some scholars.

@SK the link you gave appears to be a summary of the work of Madhukar Ramrav Yardi. Not of Sukthankar. I think your claim was about Sukthankar. Is that correct?

@SK Based on the url link you posted about the various styles in the Mahabharata: Lord Ved Vyas might have deliberately written the Mahabharata in various styles to increase the literary richness of His historical work. This is not an uncommon practice among poets. Shri Kirtivasa's Bengali rendition of the Valmiki Ramayana, which I have at home, contains (at least) two different styles of rhyme. The statistical study from Bori then just reveals that Lord Ved Vyas wrote in various styles. Does not prove the multi-layered interpolation of the Mahabharata nor does it reveal events were made up.

this is the exact quote re: Sukthankar: "He gives the credit of transforming a heroic poem of 24,000 verses dealing with the Kaurava-Pandava war into a Dharmashastra consisting of nearly one lakh verses to a band of inspired Bhargava poets who were partial to the cult of Narayana-Vishnu @estimator

@SK I will check where he said that. But it may be of interest to note that another Mahabharara scholar Alf Hiltebeitel thinks that the role of Krishna/Vishnu is central to the epic. Not an interpolation.