Kṛṣṇa, for understanding of the common people, the highest truth of Vedic literature, the highest truth of Vedic literature is Kṛṣṇa, and nothing else. You will find in the Bhagavad-gītā the Lord says, vedaiś ca sarvair aham eva vedyaḥ (BG 15.15): "The whole purpose of Veda is to understand Me." That's all. If one has understood Kṛṣṇa, then he has understood all Vedic literature. He has nothing to understand anymore. He has passed all examination.
Vedaiś ca sarvair aham eva vedyo vedānta-kṛd veda-vid eva cāham. And the Lord says that "I am the writer of Vedānta," because Vyāsadeva is an incarnation of Kṛṣṇa for writing this literature. His name is Kṛṣṇa Dvaipāyana Vyāsa. Therefore, as incarnation of Vyāsa, Kṛṣṇa wrote all this Vedic literature. So vedānta-kṛt and veda-vid eva cāham: "And if anyone understands Veda, then it is I only who understands Veda."