Reformation is an opportunity for new ideas to take hold.  I don't think you can predict what type of ideas they will be, political or religious.  In this case, the time was ripe for politicial exploration.  The Germany we have today has changed so much since then.

Critics of the Church had been questioning the power of Rome for quite some time before Luther, and as others have posted, many shared the same fate.  The excesses of the recent popes with the resale of indulgences, for example, to cover church debts caused many to question exactly what authority Rome possessed.  What protests, or "heresies" that could be mounted remained local. What made Luther's condemnation unique in Germany was that by the early 1500's, most German nobles opposing the Church could read.

Gutenberg had developed printing in Germany in the mid 1400's, and the first mass production of bibles began.  Concurrently, the literacy rate rose.  By Luther's time a few generations later, secular works, although circumscribed by the Church, were also printed.  Luther's 95 Theses was the first criticism of the Church that was printed and distributed, which meant that his "heresy" was the first widely read by those holding political power, namely, the same literate German nobles who were being unfairly taxed by the Church.

The the lives of Gutenberg and Luther, the facts of printing and religious revolution, historical forces of cause and effect, both occurring in Germany a half-century apart, should not remain obscured.

I wouldn't use the term upheaval because that implies change.  It's not like the system was changing in Germany -- it had been like that for a long time.   I would say that the political system that existed in Germany, with multiple contenders for power is what did this.

But essentially, yes.  In places like Spain, there was one strong government and so there was no one who had any incentive to help Luther get his message out.  In Germany, promoting Luther was compatible with the political goals of many of the princes.  This gave them a reason to support him and so he escaped the fate of people like jan Hus.

Germany was perhaps fertile ground for the Reformation, and indeed Luther probably would have failed there were it not for the political situation. Luther's message, although somewhat different, was not so earthshatteringly profound that it became a virtual epiphany for the German people. Indeed, John Huss, a Czech, had previously questioned the Church's teachings, and was burned at the stake for it, even though he had been guaranteed safe passage. Luther also was condemned by the Council of Worms, and would have suffered a same fate; however a sympathetic noblemen rescued him and protected him thereafter. Luther's teachings that the Pope had no special authority gave those nobles who wished to be free from the Holy Roman Emperor all the excuse they needed. They declared allegiance to Luther and his faith not for religious reasons, but because it was politically expedient.

I don't think it was particularly more susceptible to the religious part of the Reformation, but I think that it was more susceptible to the political part, which was perhaps just as important.

The German system of all these little states, each with its own ruler was really conducive to keeping Luther alive and spreading his message.  Rulers who wanted to rebel against the Holy Roman Empire wanted to keep the religious ideas of the Reformation going so that they could use them as a rallying point/justification for their rebellion.

So I think the religious ideas could have sprouted up anywhere, but I think that the German political system of the time was much more conducive to keeping those ideas alive and spreading than more centralized countries' systems would have been.