How the much maligned, "caste system" actually made Hinduism's existence possible, after the deadly onslaught of Islam

I had for long wished to write a lengthy post on how the much maligned, "caste system" actually made Hinduism's existence possible, after the deadly onslaught of Islam when on the other hand, Islam had vanquished Egypt, Syria (Eastern Roman Byzantine Empire), Persia, South East Asia (Indonesia, Malaysia) but Islam's confrontation with India and Hindus, even after more than thousand years is still a stalemate...........  Bharat Swami (भरत स्वामी) ji reminded me about "Spain, Sicily, Greece, Romania, Bulgaria, Russia, Armenia and many other eastern European countries were under islamic rule for centuries but they survived too."................. In reply to it, I have the following to submit, that Spain reversed Moorish culture first by militarily reconquering territory and then forcibly reconverting those who had taken to Islam.....Historically military and political pressure of neighbouring Christian powers  ensured survival of satellite christian population which fell under Islamic yoke, besides Christians of Eastern Europe were 'people of the book', they could be tolerated in Islamic state but not idolators.... Nowhere "pagans" have survived under Islamic rule unless they took to remote and secluded places. To which Bharat ji had to say that " ottomons/moors/tatars were as ruthless to christians as the turks/khilajis/mughals were to Hindus. Point is there are many examples where a native culture has survived and fought back the barbaric muslim rule. And most of them didn't have caste syatem.We should be proud that we also lived to tell our story, even after having as degrading a social practice as caste system.".....................But My understanding of "caste system", certainly is not that of it being a degraded system..... This is the whole point about survival of Hindus....comparison and similarity with above native examples ends there....Christian survival under Islam is not same as Hindu survival under Islam....Egypt, Syria, Lybia etc were Christian majority at the time of Islamic conquest and even in Mesopotamian Iraq, Ethiopoia, and in Arabian penisula Christians were present before Islam and survived in small pockets to this date.....but Hindus without a strong political, military and religiouslly organised Church power, survived in not only in some small pockets but throughout the geographical cultural enclave called India and despite the fact that converted Hindus had no history of not getting re-Hinduized or relieved on mass scale, unlike in the case of Eastern Europe, Sicily, Andalusia etc.....that means despite loss of political power Hindus had robust social system which withstood Islam and the case of Hindus could be contrasted with equally strong Buddhist influence at the advent of Islam in Central Asia, Afghanistan, regions of Sindh, Kashmir, Bihar, Bengal etc where we find Buddhist population was majorly converted in to Islam.....'caste system' as an open source social architecture with Varna classification, combined with, kula (clan n family origin), regional identity, and guild loyalty all rolled into one single system of "Caste", which was de-centralised and diffused enough, for Islam to not be able to co-opt social elites completely as they varied from place to place and even varied from time to time....so the socio cultural collapse was not sudden and catastrophic in case of Hindus under Islamic attack n occupation........... And it would be interesting to understand that why did Mixed Buddhist n animist tribals like Turks, Mongols, Afghans etc became vanguards of Islamic expansion after the initial energy and religious and imperialist expansionist zeal of Arabs (the original first Islamists) got extinguished?  Arabs could never penetrate India deep and same is true for Eastern Europe....it was Turks n Mongol Tartars that were Islam's vanguards.....both Turk n Mongols initially had mix Buddhist n Animist beliefs.... On the eastern front Ahoms were like Mongol Tribe, got Hinduized, Gorkhas too were Hinduized from Tibbetan Buddhist influence....they became Hindu vanguards but if they would had been Buddhist, I bet Assam and Nepal would had met Bangladesh like fate....here is my two pence of forecast....as the rate of conversion into Christianity among Buddhist influenced mixed Hindus of Eastern Nepal, Sikkim is much faster than solidly Hindu western Nepal.....We will see Christian Eastern Nepal and Sikkim within 3 decades............... I am using "caste" and "caste system" in a specialised sense, while I concede Varna as an idealist classification and "Jaat" as practical social reality are not same but "Caste" as we understand it now, (if it's meaning could be divorced for the time being from European usage of Caste with racial connotation, as in modern coinage it originated from 'castus' implying race),  'caste' serves as a fuse to socio-political stress on Hindu society....its strength is subverted as its weakness by looking at it through tinted cognitive filters of Western Colonial understanding (tainted with Abrahmic Universalism) which Indians have internalised,..... It's because of this that the seemingly paradoxical and amusing dilemma of modern India could be resolved, that either the champions of destruction of caste as an ideology are also surprisingly the greatest champions of caste based politics of patronage.... Or on the other hand, guilt trapped colonised minds of Hindus in their one sided pursuit and wish for unity of Hindus also decry caste system...... Feeling ashamed of 'caste' is a colonial legacy and is the extension of colonised social consciousness, and this assertion is supported by eminent social scientist Prakash Shah too. (This post is a compilation of my answers to a discussion on Faizan Shehzade brother's post, hence here is not a systematic exposition with academic refrences given to rigourously substantiate my assertions).

Courtesy: Ravindra Singh Basera Dev, https://m.facebook.com/story.php?story_fbid=10214504708068574&id=1146345539