"What is the reason for Il Duce's newly acquired antisemitism? Why the new laws degrading the Jews of Italy? There are hardly 60,000 native-born Jews in all Italy. Many Italians have never laid eyes on a Jew. Antisemitism played no part in Italian life until Il Duce determined to banish the Jews into a moral and material ghetto."
Oddly, no reason is given, but it seemed clear to all that Mussolini was simply doing a favor for Hitler.
This website has more on this topic.
Pictured above is the Synagogue of Trastevere - the oldest synagogue in Rome.