In 1517 the same trade roads that carried cloth and coin carried ideas — but slowly, one traveller at a time, and a bishop or a burning could stamp a heresy out before it left a diocese. Hus, the Lollards, the Waldensians all spread this way, and all were contained.
The printing press changed the arithmetic. A single shop could throw thousands of copies of a pamphlet onto those same roads in weeks. In the model each press multiplies a city's local transmission, so any town the idea reaches becomes a source that outruns the censor. Luther's tracts sold hundreds of thousands of copies in a few years.
That is why the Reformation "took" where earlier heresies died: nothing about the doctrine's appeal had to change. The medium changed the epidemiology of the idea — its reproduction number crossed one, and once past the containment threshold, suppression could no longer keep up.
The simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.