The Veda is the beginningless information self-manifest by reality itself. It was to the first entity, Brahmā, that Viṣṇu first revealed full access to it. Brahmā then verbalized it to his initial children. Those children, especially the Seven Sages (Sāpta Ṛṣi) codified his words into specific mantra, thus creating the original Yajur Veda.
Over time, the meaning of these mantra became garbled and confusing, even to Brahmā.
Vyāsa repairs this by editing. His edit creates four divisions pertaining to four aspects of sacrifice, and a fifth division for the important contextual information underlying the sacrifices. These divisions are elaborated upon over a long span of time by scholars under Vyāsa’s instruction and guidance. (Vyāsa is superhuman, although even without this, his influence and representatives could have overseen the further development of the five divisions.)
The elaboration resulted in enormous volumes of Vedic text nearly impossible for a single human to study in a single lifetime. Also, the elaboration resulted in many diverse viewpoints, difficult to reconcile. Seeing this as a shortcoming, Vyāsa set out to harmonize all the diversity, while also shrinking the enormity of the Veda into a single book of mystical codes: the Brahma-sūtra.
Upon completion, he found the codes to be too mysterious, so he set out to illustrate them using vivid and colorful stories related to Krishna and great historical personalities. This resulted in the epic Mahābhārata.
Upon completion he remained dissatisfied, for the ultimate esoteric essence of the Veda was not yet perfectly clear, even when reconciled and condensed into the Brahma-sūtra and illustrated by the Mahābhārata. Vyāsa then took the foremost Purāṇa, named Bhāgavata, and revised it in light of Brahma-sūtra and Mahābhārata. Thus he created Śrīmad Bhāgavatam, the ultimate fruit of the Vedic tree, and became fully satisfied that he had restored, and perhaps even improved, the original exposition of the Veda.
This is the answer to one of the homework questions in the second session of an online course called, “The Role of Sacred Text in Gauḍīya Bhakti.”
– Vraja Kishor