“Hinduism” as a religion erases the unique folk identities in India. It is a lazy, colonialist way to group an entire subcontinent with a stereotypical, uniform religion.

Religious syncretism in India is a very visible and real thing - not just for “Hinduism”, but also other religions in India. Casteism, on the other hand, is a effect of Brahminism - meaning that not every place in India has the codified chaturvarna (quad-caste) system - especially in the South of India, where’s there’s an incomplete caste system, comprising of Brahmin-Shudra inside, and Dalit/Tribal outside, as opposed to the Brahmin-Kshatriya-Vaishya-Shudra inside and Dalit/Tribal outside classification. In fact, there have been multiple anti-casteist movement before, like the Nath (started from my mother land), Lingayat movement (in mainland Karnataka), the Bhakti movement (somewhere in Tamil Nadu), the Adi-Dharma (in Punjab) and the Arya Samaj movement (around colonial era in Bengal) - there’s more of them, but I can only remember these.

That inertia even allowed it to not become muslim majority.

Not really - there were repeated Islamic invasions aimed to chip the wealth. Religious conversion, however, was a secondary thought. Matter of fact, there was no need for Muslims to convert Hindus in central India, because rulers did not act over religion, but over power. Many Muslim leaders in the North of India had Hindu officials in their court, they also married and did not convert their wives to Muslim, and vice versa. In fact, there’s also a case of a homosexual Muslim ruler called Alauddin Khilji, who had a relationship with his slave Mallik Kafur. Mubarak Shah, son of Alauddin Khilji, also had a male lover called Khusrau Khan. In fact, it was also advantageous for the Muslims to impose jizyah and kharaj tax.

In the place that I am from, which is the south of India, there’s a temple that is often visited by Muslims, which would probably be frowned upon by Muslims from Arab. In fact, these Muslims also take part in animistic rituals - remember how I said that “Hinduism” is a colonialist term? Yes, Tulu-folkism is what is practiced in my motherland, and Brahmins have no control over these rituals - it is the tribal groups Koragas, who organize prayers for the Shudra groups in Tulu Nadu. In the north of India, Sufism, which is a type of mystical Islamism, is the very opposite of radical Islam, and in fact, was open to the idea of “many paths, one Gods”.