According to Osho, Mahavira spoke in Prakrit because Sanskrit was an elite, over-refined priestly language used to monopolize meaning, while Prakrit was the people’s natural tongue. By teaching in Prakrit he addressed ordinary folk directly, bypassed pundit intermediaries and sterile shastrarth, democratized truth—and for that very reason the Sanskritic establishment sidelined him, even omitting him from Hindu scriptures.
He spoke in the everyday language so everyone could understand him without needing priests to explain.