…while also learning that the Renaissance was not necessarily a thing. Tumblr is for nerds; crashcourse is for nerds. This is perfect. PLUS: ninja turtles.

I agree with most of this, but it’s actiually simpler than that.  Historians who were part of the Enlightenment decided to call everything they didn’t like “Medieval” and everything they did like “Renaissance.”  Renaissance is generally considered to start with Petrarch in the early 14th century and run to the death of Elizabeth I or thereabouts.  Meanwhile things like the Great Pestilence, Bonfires of the Vanities, Pogroms, and various nasty wars were going on.  The Renaissance label was a way to pretend that these things weren’t all happening at once.  On top of this, later scholarship noticed that the influx of Classical texts from the Islamic world starts with captured libraries during the reconquisa in Spain.  You get a whole big wave of Aristotle influenced thinkers well before the Renaissance label gets slapped onto elements of the 14th century and after.  You also get innovations in technology starting in the 10th century that make a material difference in demographics and lifestyle.