Why were nobles important to foublism?

You probably want to know about their role in feudalism. The nobles played an important part in feudalism because the feudal system ensured the king of their loyalty and support, especially in military matters: it was the nobles who at their own expense provided the king with soldiers in case of war and who themselves served as his commanders and officers. In return, the king rewarded the nobles for succesful service by providing them with land.

This served the double purpose of providing them with a regular source of income. And at the same time, the king ensured himself of people who would rule those lands for him, dispense justice and collect taxes.