Question

why did aryabhatta invent 0

Answer 1

Zero could have been invented for easier calculations and abstract mathematics. There is a saying by an eminent mathematician that "Today's abstract math is tomorrow's applied math".
Following in the same lines, Zero as a entity means nothing, as we already know now. But the early concept of giving a symbol to nothing would have been considered abstract then. However, for easier calculations as we can see now Brahmagupta could have created a Zero out of nothingness(Śūnyatā). The cultural and religious backdrop of Hinduism preaches everything starts from nothingness. So, he might as well given that 'nothing'-ness a symbol. And for Aryabhata, he gave the rules to use 0 in mathematical operations, not the number itself.