A bottleneck in cultural transmission

Yet what any individual in the Frankish Empire [of the 8th century AD] got to read was often a matter of chance. The full range of classical literature was by no means still available in its entirety. Much had disappeared and had been lost forever. Because of lack of knowledge of the language, almost everything in Ancient Greek had by now vanished from the educational canon of the Latin people, insofar as those works had not been translated or popularized in Latin in the classical period or late antiquity. Indeed, the image we have of ancient Roman literature has to this day been fundamentally shaped by the Carolingian age's eagerness to read such works. Every piece of Latin literature that this period managed to get hold of and save has been preserved for posterity; conversely, the works it shunned or never got to know have been lost forever.

-- Johannes Fried, Charlemagne (Cambridge, Mass. : Harvard University, 2016), pg. 274.