A single celebrated collection can become the symbol of a whole region's learning. That makes it easy to miss that it was only one of many centers. Scholarship spread across many towns and teachers, not one capital of knowledge.
Calling a continent a place of oral tradition can erase evidence of long-standing written scholarship. Surviving manuscripts disprove the label, which is why they become powerful symbols. They prove a tradition of written learning that outsiders long denied or overlooked.
Learning was sustained by a recognizable class of scholars and clerics, together with their schools and teaching system, not by isolated geniuses. This class was also the one that brought new groups into the religion. Those who could read and write the scholarly language were the agents of conversion.