That article relies on the Aryan invasion/migration theory, which has now been discredited by modern genetic studies. See
The peopling of India - Pragati
You cannot just discard Aryas, think of the word ARYABARTA in old Hindu scriptures. North India was called Arybarta, and this word was not coined by a British or a German. Whether they came from the central asia or through west asia is a matter of debate. But, just because there is a debate on the matter, it is not a good logic to refuse the main content of an article.
Issue here is the caste infested Hinduism, where the Brahmins wielded too much of power that they used to persecue the local Bangali Budhists. Bengal was more Budhist than it was Hindu. Until the end of Pal Dynasty, Budhism remained strong here. But after its demise in 1095 by Vijay SENA, State patronage for Budhism was revised to the patronage of Hinduism. Obviously, the caste system was incorporated in it. During the next hundred years until the arrival of Turkic Muslims in 1203, Brahmanism had been fully restored in Bengal.
However, this was not accepted by the Budhists of Bengal. During many centuries of Budhist teaching many high caste and low caste Hindus accepted this religion, which was not infested with a caste system. These people were forced to accept a lower place in the Hindu society during the Sena rule of more than a hundred years.
When the Muslims migrated to Bengal, these people welcomed the adventurers. I have read a poem written in those days that appreciates these foreign Muslims as their saviours. In the long run, many of these Budhists accepted Islam, which also does not believe in the JAT PAT system.
In old days, a lower caste Hindu was not even allowed to visit a temple, he was not even allowed to hear the Sanskrit MANTRA read by those Hindu Brahmins. A Sudra would have been killed by pouring MOLTEN LEAD in their ears for a simple offence like that, such was the harsh punishment. The Sudras were taught since their childhood to be content with their lives as SUDRA, because if they do so they would be re-born in a higher caste next time.
Sudras were fully illiterate, therefore, they were not enlightened. For them to accept their present faith as SUDRAS was the best way to go to paradise. They had been totured into such a corner by the Brahmins that they had no alternative vision which can change their fate. How they can change their religion when they were just a dumb group of people forced into believing in superstitions?
They used to think, probably the presnt day Sudras too, that the Brahmins can destroy everything by blowing out fire from their mouths. Can someone think that these were the people most ripe to change their religion? Only the enlightened ones have the inner knowledge to understand the difference between a bad and a good religion.
This is why there established a BRAHMA SAMAJ in India during the British Raj, which was composed of the most learned families of the Hindu society. Rabindranath Thakur's family was one of them. Do you know, that this family had been branded as 'PIRALI' (Pir Ali) Brahmin and was made the social outcaste in the Hindu society? Why? Because one of their ancestors had shown the audacity of accepting the invitation of one Muslim Pir named Ali during the Muslim period. This Tagore family could not even marry their daughters off to any Brahmin family. So, they used to adopt a Brahmin child from a poor family and then marry off one of their daughters with him at adulthood.
In an atmosphere like this when the Hindu society was ready to discard Hindus to protect the Hindu religion, one can expect the gradual conversion of enlightened people to a different faith where they do not have to bear such inhuman stigma and insult by the religious leaders. I must note one thing here. Muslims were more worriors than administrators. Law and Defence departments were under the Muslims, but all other govt Departments were either captured by the educated Hindus or Budhists.
Many of these govt servants also ultimately accepted Islam. Can an illiterate person, Brahmin or Sudra, can hold such a position? Since they were literate, therefore, it is a certainty that they were the higher caste people, and not Sudras, who were not allowed to get education.
So, it is preposterous to think that the educated Budhists or the higher caste educated Hindus did not accept Islam, but the illiterate Sudras accepted it. It was just the opposite. I know many Muslim families near my ancestral village with family titles of Thakur, Pal, Biswas, Singh and some others. My question is if Sudras had accepted Islam in Bengal, then why it is that there are so many Sudras among the Hindu Bangalis and why there is almost no Budhists among the Bangalis?
After the Turkish Muslim migration to Bengal, the Budhists here flocked to that faith. This Muslim group became so strong a core that not only that they were the dominating force in the eastern part of india, but also that these Muslims resisted Delhi subjugation for many centuries. At one time, they even took over Delhi under the leadership of Sher Shah Suri.
The truth is, all the Budhists and many of the high caste Hindus in Bengal had accepted Islam and the Sudras remained in their old religion, where they are still suffering at the hands of so-called high caste Hindus. What a religion is this Hinduism? When all other religions try to unite people under one banner, Hinduism is the only religion that makes divisions among themselves, creates barriers and teaches to hate each other.