Here's why:
* Prakrit languages were the common languages of the people in India at that time. They were derived from Sanskrit and were spoken by the masses.
* The Mauryan inscriptions are mostly in Prakrit languages. The famous Edicts of Ashoka, which were inscribed on rocks and pillars across the empire, are primarily in Prakrit dialects, particularly Magadhi Prakrit. This suggests that Prakrit was the language of administration and communication within the empire.
* Sanskrit, while a highly esteemed language, was primarily used for religious texts and rituals. It was not the everyday language of the people.
However, it's also possible that there were other languages spoken within the empire, depending on the region. The Mauryan Empire spanned a vast territory with diverse populations.
Therefore, while the exact language spoken by the Mauryans is unknown, Prakrit languages were likely the dominant languages of the empire, with Magadhi Prakrit being particularly significant.