In large part, the printing press.
Martin Luther could be credited with the world’s first mass media driven revolution.
“Printing was essential to the creation of Martin Luther, but Luther was also a determining, shaping force in the German printing industry,” Pettegree writes. “After Luther, print and public communication would never be the same again.”
When Luther nailed his 95 theses to the door in the Saxon backwater town of Wittenberg, moveable type was something like the computer in the 1960s, a useful and expensive tool used by academics and elite institutions. “Most customers were churchmen, scholars, or students, with a smattering of rich collectors from the nobility,” Pettegree explains. “Consequently the first printers aligned their production to the established best sellers in these customers’ favored fields,” typically works that were “long, expensive, and in Latin” and written by long-dead authors. Wittenberg’s only print shop produced ugly, sloppy copies of the theses of local university students, another mainstay of the 70-year-old industry.
As “Brand Luther” makes clear, Luther realized the untapped potential of print as a mass medium and used it to broadcast his message to lay readers across the German states, bypassing the traditional gatekeepers via this new social media. He responded to the first scholarly criticism of his theses not in Latin, the language of scholarship, but in German, with a clear, straightforward 1,500-word essay that could be read aloud in 10 minutes. It fit perfectly into an eight-page pamphlet that could be quickly and cheaply printed and reprinted, each copy using but a single sheet of paper, folded in quarto. “It was an instant publishing sensation.”
By 1519, this unknown monk had become Europe’s most published author, his 45 original compositions republished in nearly 300 editions. Realizing the limits of his local print shop, Luther personally lured a top printer from Leipzig, pairing him with the talented illustrator Lucas Cranach, whose elegant woodcuts adorned the soon-to-be sought-after “Wittenberg” editions. Cranach even created a modular woodcut for use in title pages, the center of which could be swapped out for each new book, allowing even modest pamphlets to be beautifully adorned.”
Quotes from this Washington Post article: https://www.washingtonpost.com/opinions/the-power-of-luthers-printing-press/2015/12/18/a74da424-743c-11e5-8d93-0af317ed58c9_story.html?utm_term=.11a2c0b75997
I personally own Pettegree’s book, “Brand Luther,” and would highly recommend it as it goes into great detail to answer your question. You can buy it here: https://www.amazon.com/Brand-Luther-Unheralded-Europe-Reformation/dp/1594204969/ref=nodl_