The Renaissance appears in Firenze in the early 1400s as a sort of protest against the “barbarians in the north” (the HRE).
Now, that's quite a simplification. There were so many factors that contributed to the emergence of the Renaissance, like Italian city-state culture with its republican governments and strong orientation towards trade and commerce, strong Greek influence over about 150 years, the Black Death, and above all: the discovery of Neoplatonism (as opposed to the standard Aristotelism of the medieval universities).
Of course, there was also a kind of Italian proto-nationalism against the Germanic "barbarians", that had destroyed the Roman Empire in the West, but that's just one factor among many and not even the first and foremost one.
For example, Mantua under the Gonzaga, Siena, Urbino or Ferrara under the d'Este were also early centres of the Renaissance (and not just 40-50 years later) and they had been staunchly Ghibelline cities for a long time.