The decline of Sanskrit started significantly before the invasions. Think of the Sanskrit bodies of literature. How many important ones were written after 500B

The decline of Sanskrit started significantly before the invasions. Think of the Sanskrit bodies of literature. How many important ones were written after 500BC, vs before? Most of Indian literature after that period was in various forms of Prakrit, Magadhi, Pali, proto-Tamil. Creation of new literature strongly corresponds with how much a language is being used.