After careful consideration (and banging my head on my desk a dozen times) I have 3 very thoughtful, very plausible theories to this hire.
1. Mike Riley will hire Scott Frost as his OC/AHC and exit within 3-4 years leaving Scott with his dream job and a stacked cupboard. (could be several struggling seasons until then).
2. Eichorst looked at the list of requirements given to him by HP and the boosters and said, OK, you want to make me fire a 9 win coach? this guy has everything on your list, good luck with that and FU!
3. Eichorst is still in leagues with Wisconsin and secretly hopes we plummet into the abyss that is/was Nebraska mediocrity/bottom of the barrel. Leaves in 2 years (before we fire this new guy) and takes his place at the Throne in Madison post Alvarez.