Please answer a question about the following article about Utrecht:

When the Frankish rulers established the system of feudalism, the Bishops of Utrecht came to exercise worldly power as prince-bishops. The territory of the bishopric not only included the modern province of Utrecht (Nedersticht, 'lower Sticht'), but also extended to the northeast. The feudal conflict of the Middle Ages heavily affected Utrecht. The prince-bishopric was involved in almost continuous conflicts with the Counts of Holland and the Dukes of Guelders. The Veluwe region was seized by Guelders, but large areas in the modern province of Overijssel remained as the Oversticht.

What hapend when Frankish rulers established the system of feudalism
the Bishops of Utrecht came to exercise worldly power as prince-bishops