Actually they did, the Emirate of Bari. However, not surprisingly, it was rather short lived, lasting only about thirty years.
And shortly after was the great Aghlabid (Muslim, Arab-Berbers from Tunisia) invasion of Italy which culminated in the siege of Benevento. Had that city fallen, most of southern Italy would have gone with it. The Aghlabids were
much more powerful than the Arab pirates who established themselves in Bari. The Lombard rulers of the south were terrified when they heard of the incoming invasion, and with good cause. The Aghlabid army was massive, and posed the greatest Muslim threat ever to southern Italy.