Before I answer the question, you need to know that Brahmin and non-Brahmin scholars have openly started to declare that there is no such religion called Hinduism. The word/term ‘Hinduism’ is an English term which is alien to Indian religions and is not a religion.
Hinduism was a name given by the British in the early nineteenth century to a ‘group of religions’ that then existed in British India. There is no religious text of ANY religion that contains a word which, when translated, means ‘Hinduism’. Nor does any such text mention words that means ‘Hindu’, as a follower of any religion
Muslims, Sikhs, Brahmins, Buddhists, Jains (and other minor religions in that area) were ALL collectively labelled Hindu as a geographical identity
Because Hinduism is not a religion, the largest religion in India today is Islam. Due to not having this understanding (and sometimes for political reasons), Islam is portrayed as a minority religion in India. There are more Muslims in India than in Pakistan, an Islamic state.
The following may come as a surprise to you.
Three main reasons why the Brahmanic religion (assumed by you as Hinduism) did not spread to other parts of the world:
1). The religion of the Brahmins, Brahmanism (which you mistakenly thought was Hinduism), is a minority religion in India which is only followed by approximately three percent of the Indian population.
2). Just as in Judaism, you have to be born as a Jew in order to be called a Jew; similarly, one is not called a Brahmin unless one is born as a Brahmin.
3). The religious texts of the Brahmins were written in an artificially created language, Sanskrit, most probably for secrecy because the texts contained laws and strategies for controlling the masses. These texts were not meant to be read, heard or spoken by non-Brahmins. If anyone from the lower classes, violated the strict code of conduct of the Brahmins, they were punished accordingly often leading to death.
These are the reasons why Brahmanism, which I assume you referred to as Hinduism, did not spread to become a world religion
