After 20th-century civilization was destroyed by a global nuclear war, known as the "Flame Deluge", there was a violent backlash against the culture of advanced knowledge and technology that had led to the development of nuclear weapons. During this backlash, called the "Simplification", anyone of learning, and eventually anyone who could even read, was likely to be killed by rampaging mobs, who proudly took on the name of "Simpletons". Illiteracy became almost universal, and books were destroyed en masse.

From the Wiki.

It's what is left after tyranny. A bunch of dunces milling around sifting through rubble.