This is a common refrain but in reality I'm not sure it made much difference. Papyrus just doesn't age well and most manuscripts from this era would've been on papyrus.
What really decided what texts survived and what didn't was monastic traditions in in the Dark Ages and Middle Ages [1]. At this time, a monk might spend their entire life transcribing a particularly long manuscript. The materials were also expensive. So monasteries were selective in what got retain and unsurprisingly it skewed heavily to texts of religious significance and then to texts of significance to, say, Roman and Greek tradition and history given that monasteries were European.
[1]: https://spokenpast.com/articles/medieval-monks-erased-preser...
Thanks for sharing. Maybe not as common as you think. I never heard that before.
It was a little before that even.
Greek was the language of most fields of learning besides law in the Roman Empire. But the Greeks themselves wrote works on these papyrus scrolls that crumbled fast, so anything not actively used by the Romans was quickly lost.
There's a good chance that if the papyrus scrolls in any library (Alexandria or otherwise) weren't being copied regularly they were crumbling even before they burned or were lost to time for other reasons.
Towards the end of the Roman Empire, a few philosophers took the time to transmit Greek knowledge in Latin as knowledge of Greek faded in western Europe. What these guys happened to translate was the basis of most of European learning in philosophy, math, and other fields for centuries.
But they weren't monks (the most famous, Boethius, was not Christian either but a lot of later writers thought he was), the monks in scriptorium came later and grew slowly.
St. Benedict said that monks should be taught to read and do so regularly, which required copying books, but he prioritized physical work (to create self-sufficient communities) and prayer. But future Benedictines responded to the incentives of the time and began scaling up the copying and doing less agricultural work as the years went on.