I know that the Church was one of the biggest preservers of ancient texts through their copying initiatives at monasteries but I'm curious just how these ancient sources were seemingly forgotten and then rediscovered all of a sudden during the Renaissance. Did a monastery/church just decide that a certain document wasn't worth copying anymore and threw it in a corner in the library where it was forgotten? Do we have any actual original copies that were not reproduced by the Church that were stashed in their libraries or are they all later copies? And how were these documents just kind of forgotten? Did people stop caring what the ancient writers said for a while and so didn't see a need to keep them in the front window so to say?
The Renaissance didn't so much rediscover archive material within Christendom, as it was catalysed by an influx of works and treatises from the Byzantine and Ottoman empires.
A similar renaissance occured in the twelfth century following the reconquista of Toledo in 1085. The library there had a massive collection of classical texts which had fallen out of popular knowledge in most of Europe, since the knowledge of Greek had become particularly rare since the decline of the Roman Empire. At Toledo, however, the vast majority had been translated into Arabic, which was far more commonly spoken, especially by Christian clerics in Spain. This allowed a vast number of 'lost' works to be translated into Latin from Arabic far quicker and more easily than had they been in their original Greek, and a large amount of Classical philosophy, science, theology and learning entered into Western Europe as a result. The later renaissance was a similar occurence.