Why did protestantism flourish in northern renaissance europe rather than southern renaissance europe

First of all, let us state the obvious. Martin Luther was from Germany. Secondly, Italy is the center of Catholicism, with Rome as the seat of the pope. Also, other kingdoms did not want risking excommunication from the Catholic Church, as the pope was a very powerful figure one should not mess with. Most of the supporters of protestantism were minor German princes who had nothing really to lose.