I'm only 20 minutes in, but this is a really fantastic video. Thanks for submitting it, Pillager.

Good watch, very informative.

So, the short version.

Inheritance of the Greek and Roman empire's infrastructure allowed trade to flourish and with trade came exchange of ideas and knowledge.

Infighting between intellectual schools led to a king making a martyr out of an opposing philosopher which created rebellion, infighting and revolution.

Not taking the crusades seriously was a huge mistake and only furthered said revolutionary anti-intellectual thinking.

Then a king thinks its a great idea to declare war on the Mongols, with predictable results.

Then another king thinks its a great idea to ask the Mongols for help, with predictable results.

Meanwhile Europe figures out how to eliminate the need for overland trade and the money to the Middle East gets cut off.

TLDR: Globalization brings knowledge, war and insular thinking brings the opposite.

This guy was wrong about Trump working on infrastructure but he's not the worst youtuber.