One would suspect that given the alacrity with which they shed their affiliation with the hierarchy of the day, that they might have been kind of upset prior to Luther knocking over the applecart. In any event, the numbers were huge, considering the lack of mass communication.
And the Germans had been Christians since at least the time of Tertullian - he mentioned Christians among them even then, which should be no suprise since the Apostles went off as fast as possible to all the peoples that could be found. Thus St. Thomas going to Persia and India, and St. Andrew to Scythia.
As to the peacefulness of later conversions, I'm not sure what you are referring to. In Iceland, for example, the conversion occurred by a vote of the Althing, and the people accepted it.
The Germans did not "bail out in droves". Some German Princes did, and the Reformation settlement of the religious wars dictated that the Religion of the Prince became the Religion of the Realm. Most people did not voluntarily leave the Church, nor did most ecclesiastics, which is why Luther's German Church had no Bishops apostasize to it. The peoples themselves were forced to become Lutherans by the Princes and Pastors.