> The Dark Ages started when Christianity spread through most of Europe.

1000-1400s AD was a period of extremely rapid (by historical standards) economic, societal and technological progress. Just compare with the highly stagnant (in relative terms) Roman Empire between 0 AD and 400 AD. It was the opposite of the dark ages…

500-800s AD were not great, but plague, climate change and extreme political instability likely had a bigger impact on that than Christianity…