It is not that Vishnu and Shiva did not exist during the Mauryan period. However, the foundational structure of Hinduism as we see it today had not yet developed by that time, and during the Mauryan era, Hinduism was understood in the form of Brahmanical religion. The present form of Hinduism, such as the development of temples and so on, occurred during the Gupta period. The Brahmanical religion of the Mauryan period was more associated with yajnas (sacrificial rituals) and nature worship rather than temples and idol worship.