They're basically in the same position that LSU fans were after Ed Orgeron had a couple of mediocre years after taking them to the promised land. They just want some order restored.
I'd guess that Brian Kelly would do decently at Penn State, getting them back to regular top 25 placement, and challenging for top 10 positioning, but in the end, he wouldn't be much of an upgrade over James Franklin.
I don't see his being able to beat tOSU at least one out of every four times.