Why might the period of time after the classical period be known as the Middle Ages?

The adjective "medieval" (or sometimes "mediaeval" or "mediæval"), meaning pertaining to the Middle Ages, derives from medium aevum. Medieval writers divided history into periods such as the "Six Ages" or the "Four Empires", and considered their time to be the last before the end of the world.

Explanation:

"the attempts of the proletariat to rise above this abasement"

a 3 branch government