hi! could you specify which language/culture/region you're asking about? thanks!

I can only speak for English medieval literature. But what can be said for it is this:

The late twelfth and early thirteenth centuries were the nadir of the English literary and scribal tradition, but this is largely for reasons specific to England, which do not reflect upon the remainder of Europe. Namely, the rise of Anglo-Norman as the language court and culture.

Where the 9th and 10th centuries had seen English treated as a language of scholarship, culture and civil record, the 12th and early 13th left the inheritors of their corpus feeling happy if they could be so lucky as to come by some rural priest's homiletic mutterings or for example a guide to how to Nun properly.

This is traditionally seen as turning around in the mid-14th century. The Black Death serves to flatten the social hierarchy in various respects in the mid 14th century, with a collection of consequent social disruptions. These are not specific to England. Peasant revolts, for example, occurred throughout Europe. And in the 14th century, we get the Gawain poet and Chaucer making indelible marks on the English literary tradition.