As ever, people assume that because written materials are lost, there's a conspiracy at play ...
It's worth noting there is not one Renaissance – scholars generally identify:
The Carolingian Renaissance
(8th and 9th centuries),
The Ottonian Renaissance
The Medieval Renaissance
The Italian Renaissance
All were marked by a period of renewal in the arts, literature, architecture, education, etc.
Meanwhile we had a 'Little Ice Age', pandemics and other stuff to deal with.
On the downside, with the collapse of the Empire and the emergence of European dynasties and nationalism, wars become really something awful.
In the Dark Ages video above, the narrator talks of Petrarch – but he was a romantic who idealised Greek and Roman culture with scant actual knowledge of it. Meanwhile we had Platonism and Aristotelianism alive and well in the universities – but he was alive during the Black Death, a plague that killed 30-60% of the European population, so any other time probably looked more inviting ...
And the old saw of the average age being 30 – again, wrong. Child mortality brought the average down, but if you survived to 20, you could look forward to your three score and ten. Child mortality was no better in Greek and Roman times, nor really improved until more recent times.