Is the Aryans Caste System the root cause for coversion of thousands then tat sum to milliions now?

The Aryans, the Indo European peoples who left the Central Asian Steppes and ran roughshod over the Indian Sub Contienent as well as what is now Iran, Iraq, Turkey and all of Europe, did so so long, at the very dawn of recorded to history, that to blame them for conditions that exist five thousand years latter seems a little lame. Yes, they were invaders and conquerers. Guess what? Five thousand years ago, everyone was an invader or else they were invaded. There were no cultures that live up to our romantized vision of a perfect golden age of peace of wisdom. So many things have happened since, including the Mogul invasions and British Conquest. If the Aryans hadn't introduced a caste system, would Indians today avoid converting to Islam or Christianity? Maybe. But Maybe not. Who can what shape Hinduism would have without the influence of the Aryans? Perhaps the non-Aryan version of Hinduism would lose just as many converts to the Modern invaders becasuse of some other factor. It's fun to play "what-if" games with history, but the farther back in history you go, the harder it is the really be able to anticipate the consquences.