Exactly. There is a very, very small group of schools that have the ability to poach successful power 5 coaches away. Nebraska isn't one of them, which isn't a slight. 99% of schools are in this group.
Lets even look at the "blue bloods" of the college football world and their most recent hires:
Michigan - picked up Harbaugh after he was being shown the door at the NFL. Harbaugh being an alum is the only reason this happened. Clearly would not have happened if Harbaugh was in a secure position in the NFL.
Ohio State - hired Urban from the booth.
Alabama - hired Saban away after two mediocre seasons in NFL.
Oklahoma - hired a coordinator
Texas - hired a guy with 2 years of experience outside the Power 5
Notre Dame - hired a guy from outside the Power 5
USC - hired a coordinator
Florida State - hired a coordinator
Penn St. - hired a HC with 3 relatively successful years at SEC doormat
Almost nobody hires away other power 5 coaches with sustained success because, frankly, there just isn't that many of them.