The Vedic knowledge is given to everyone, because Kṛṣṇa is in everyone's heart. Sarvasya cāhaṁ hṛdi sanniviṣṭaḥ (BG 15.15). He's sitting in everyone's heart. But one must be qualified to receive the knowledge. Kṛṣṇa is helping us from within. He is giving us knowledge from within. Without also. So without, He's spiritual master. And within He's Supersoul, caitya-guru. In this way, we are getting knowledge.
So Brahmā is getting knowledge from Kṛṣṇa, and Brahmā is distributing Vedic knowledge. Therefore he's authority. We, we belong to the Brahma-sampradāya, our this Caitanya Mahāprabhu's sampradāya. There are four sampradāyas: one from Brahmā; one from Śrī, Lakṣmī; one from Śambhu, Lord Śiva; and one from Kumāra. Kumāraḥ kapilo manuḥ. So there are four Vaiṣṇava sampradāyas. So we have to approach the authoritative representative of Brahmā, Kṛṣṇa. Then we can get the real knowledge.