Passage: The Holy Roman Empire (the successor state of East Francia and then Lotharingia) ruled much of the Low Countries in the 10th and 11th century, but was not able to maintain political unity. Powerful local nobles turned their cities, counties and duchies into private kingdoms, that felt little sense of obligation to the emperor. Holland, Hainaut, Flanders, Gelre, Brabant, and Utrecht were in a state of almost continual war or paradoxically formed personal unions. The language and culture of most of the people who lived in the County of Holland were originally Frisian. As Frankish settlement progressed from Flanders and Brabant, the area quickly became Old Low Franconian (or Old Dutch). The rest of Frisia in the north (now Friesland and Groningen) continued to maintain its independence and had its own institutions (collectively called the "Frisian freedom") and resented the imposition of the feudal system.

Question: Who created the private kingdoms?
local nobles