One of the challenges is that Indian intellectual tradition didn't highly prioritize keeping track of or attributing authorship to ideas, so often they just kind of floated around or were put into the mouths of sages or deities. It's hard to disentangle the line between religion and philosophy in these contexts. So much so that a lot of religious scholars argue that the very concept of "religion" and how we talk about it is inextricably tied into Christian cosmology and ideas of divinity and we either need to take explicit steps to broaden the definition or do away with the term altogether.