You need to read History again. People coming from the west ruled you for hundreds of years because your pristine as well as brave Brahmins could not stop them. Consolidation of india, as India was undertaken by those who came from the west, otherwise, as Churchill quipped that, "India is just a geographical entity. It is no more a country than the equator."
From Patna to Taxila has now moved westwards to Wahga, and there it rests. It wont change as the Vedic prophecy of "Fire From the Sky" has come true, and fire from the sky will hurtle towards earth if an attempted crossing of Wahga in undertaken.
This is the time to introduce you to the cunning and deviousness of the quintessential Brahmin.
You can only be born a Hindu, you can't convert, right? Leaving aside those bizarre Arya Samaj rites which are so PHONY.
Wrong.
If you were a mediaval Scythian, or Pahlavi, or something like that, you got a choice. For a small fee to your local priest, you could be re-born into the Hindu religion. You could be born of fire, of the Sun or of the Moon. You then became a prince, either Agnivanshi, or Suryavanshi, or Chandravanshi. And you became a bona-fide paid up member of the Brahmin Benefit Society.
Whole tribes vanished and re-appeared. Some of our most ferocious campaigners against the Turks were these converted and re-born central Asians, either Scythian, Parthian or Tocharian.
For those left with a forlorn feeling, this happened on all perimeters.
In the east, the ferocious Ahom were Sanskritised. They became enthusiastic Hindus. So, too, the Manipuris.
In the south, the Tamils swept through very wide swathes of south-east Asia, building a composite culture which had Borobodur and Angkor Vat as their mementos. From Burma to Indonesia, and out to Korea, there was a several century long swell of Indian culture (India as in Megasthnes, not as in IVC).
We all know what happened in the north. Tamang, Gurung, Magar, were all Tibetan tribes, speaking their own 'kura', not Gurkhali. They became the most ferocious fighters for Hinduism that the sub-continent has known, bar none. It was not just that they looked outwards. Many don't know, however, that Tibetan rulers ruled over extensive parts of northern India.
So it is completely erroneous to think that the Indian social system was inflexible, and not able to cope with violent change. Or that it was leaderless.
ajtr's Brahmins coped - as long as they had to deal with polytheists.
When they faced a monotheistic religion, they flexed; the Syrian Christians have lived in Kerala in comfort from the 1st century onwards. The Muslims in Kerala preceded Mohammed bin Qasim and lived very peacefully in perfect social harmony from the 7th century onwards. Finally, for the pathological case of the Turks, the response was devastating, but it took time. Five centuries, more or less.
No other civilization coped so flexibly and smoothly with external aggression, other than the Chinese. They did even better, but that is another story.