I think that a crucial element is that Italy is extremely diverse culturally; the language known as Italian is based on the Florentine dialect, which was selected for reasons of soft cultural power after unification.

The language of every country has different dialects which may rise to the level of languages, but Italian has 34 very distinct "dialects" which are really so diverse that they count as languages to the point of mutual intelligibility. I don't know about Germany (I am British) but I know that while a Shetlander and a Geordie (for example) may misunderstand one another, with good will they can make themselves understood.

But if they don't speak the official Italian and only have their own native dialect, a Barese and a Piedmontese, or a Sicilian and a Tuscan will not have a clue what the other is going on about. These days most people in Italy speak Italian (ie the official dialect) as well as their own, but it has taken time to get there.