Why did many German princes supported Martin Luther?

Answer 1

German princes supported Martin Luther's idea because some shared the same beliefs and others just supported for selfish reasons.

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Answer

In England, Henry VIII declared himself head of the Church, and thus confiscated all the Catholic Church's property, distributing houses and land (and effects) to his nobility as a reward for good behavior. In the Holy Roman Empire, the princes of different kingdoms differed in belief, but one over-riding belief in those that turned against the Church was that they would prefer to keep all their income themselves instead of supporting a Pope in Rome. Those that accepted Martin Luther's urging to become "Evangelists" - his term for his new Church, emphasising a return to the purity of the New Testament - as rewritten and interpreted by Martin Luther) became defacto head of the Church's in their kingdoms - gaining an immense amount of land, buildings, income, and effects at practically no effort - a stupendous reward to apostatize!

Answer 2

Not that I am against the Catholic Church, but at that time, the Catholic Church was corrupt. The sale of "indulgences" is one example. Also, some nobles who donated their money for the next Crusade were angry as it never materialized. Some people, like Martin Luther, believed that a reformation is necessary and began a campaign. Luther's ideas were much more easily accepted than Catholic's so he had mass support.