The Governor of Chaldea realized that he made a mistake in not recognizing Hinduism.
When it was revealed to the Governor of Chaldea that Hinduism was in fact a serious religion with too many faithful to treat in this way, another solution had to be  Hindus, along with Parsis who had fled an earlier Muslim persecution in Persia, were given the privileged status of dhimmi, dues-paying non-believers.