Srimad-Bhagavatam: Canto 1 - Chapter 1 - Verse 3


जिज्ञासितं सुसम्पन्नमपि ते महदद्भ‍ुतम् ।कृतवान् भारतं यस्त्वं सर्वार्थपरिबृंहितम् ॥ ३ ॥


jijñāsitaṁ susampannamapi te mahad-adbhutamkṛtavān bhārataṁ yas tvaṁsarvārtha-paribṛṁhitam


Your inquiries were full and your studies were also well fulfilled, and there is no doubt that you have prepared a great and wonderful work, the Mahābhārata, which is full of all kinds of Vedic sequences elaborately explained.


The despondency of Vyāsadeva was certainly not due to his lack of sufficient knowledge because as a student he had fully inquired about the Vedic literatures, as a result of which the Mahābhārata is compiled with full explanation of the Vedas.