On what basis did Indian classical Sanskrit novels develop?

Classical Sanskrit novels are developed on the basis of two epics, classical Sanskrit narrative poems and folk stories. The earliest existing works of this kind were produced in the 6th and 7th centuries, namely, Su Yidu's Biography of Immortals, Bona's Biography of the King of the Forbidden City, Dandin's Biography of Gadanbeli and Biography of Ten Princes. They inherit the secularity of folk stories in subject matter, the framework structure of two epics and folk stories in narrative mode, and the style of classical Sanskrit narrative poems in language and rhetoric. But on the whole, classical Sanskrit novels are not as developed as poetry and drama.