A lot of things, it was a lot of things. Your are describing the entirety of the Dark ages, High Middle Ages, and Late Middle Ages.
At times Charlemagne conquered most of Europe including all of north Italy.
At times there were seas of tiny feudal lords controlling various microkingdoms.
At times the Eastern Roman Empire (Byzantine) reconquered much of Italy.
At times the Holy Roman Empire regained control of much of the north.
The papacy grows in power and land.
Merchant republics grow untill the early modern period.
A LOT happens in Sicily.
A lot of things happen over ~1000 years.
If you want any more detailed specifics just ask, <3