The Digha Nikaya's length and its frequent staging as debate with prominent outside figures has made it a primary source for understanding the intellectual and religious environment the Buddha's teaching emerged into and argued against, since several suttas preserve detailed, if polemically framed, summaries of contemporary rival philosophical and ascetic positions that survive nowhere else in comparable detail.
The Mahaparinibbana Sutta's outsized importance within Buddhist tradition reflects a broader feature of the early canon: the Pali suttas overwhelmingly record what the Buddha taught rather than narrating his life as connected biography, so this single extended account of his final journey and death has functioned, across the whole history of Theravada Buddhism, as the closest approach to sustained hagiographical narrative the earliest canonical layer provides, later supplemented by much more elaborate biographical material composed centuries afterward.
Tradition holds the entire Digha Nikaya, like the rest of the Sutta Pitaka, was recited communally and verified by consensus at the First Buddhist Council shortly after the Buddha's death, then preserved through disciplined oral transmission for roughly four centuries before being committed to writing in Sri Lanka, a transmission method scholars regard as broadly reliable for a text of this length and importance, even while acknowledging that some material likely was added, reordered or lost across those intervening generations of purely oral recitation.