Population density fostered literacy, the Industrial Revolution « Per Square Mile

“The Industrial Revolution was fostered by a surge in literacy rates. Improvements in reading and writing were nurtured by the spread of schools. And the founding of schools was aided by rising population density.”

I don’t understand how mass literacy triggered the industrial revolution. You don’t need to be literate to operate a machine, only to invent one. And for that you only need the literacy of an elite, not of the masses.