You do realise that Preislamic Indonesia, Malaysia, Prebuddhist Myanmar, Thailand, Cambodia and parts of Vietnam and the Phillipines were overwhelmingly Hindu? Bali remains Hindu, and Hindu gods continue to be worshipped in Indochina. The Ramayana remains a very important story in Javanese culture. Modern Hinduism may not put much effort into proselytising, but many ancient sects did, and many modern Hindu sects are quite willing to accept converts. Which makes sense, as it is an amalgamation of the belief systems of the people of a subcontinent with 3 major language families (Indo-European, Dravidian and Sino-Tibetan) and over a billion people.I doubt that. Hinduism has too strong and rigid,an ethnic component compared to the European Pagan religions which were more Universal and kind to others to be more inclusive. So the European Pagan religions and cultures would have a better notable effect on the World if they spread at large than other Indo-European religions is what is my opinion.
The nearest equivalent belief system that comes to mind is the heavily syncretised paganism of the Roman Empire, that blended Etruscan, Greek, Egyptian, Celtic and Semitic gods. Give it a philosophical underpining as enduring and consistant as Hinduism has, and it could probably have spread out in the same way, absorbing local pantheons as it went. There was already a shared goal among many philosophical schools, ataraxia, the absence of suffering.