In 2014, Nebraska firing Bo Pelini started a chain reaction that led to three sitting Power 5 head coaches taking other jobs. Nebraska hired Mike Riley away from Oregon State to replace Pelini; then, Oregon State somehow hired Wisconsin head coach to replace Riley; and, finally, Wisconsin filled its vacancy by hiring Pitt head coach (and former Wisconsin offensive coordinator) Paul Chryst.
That single offseason equaled the total number of Power 5-to-Power 5 head coaching moves in the five years since. All three of those occurred after the 2017 season, when Jimbo Fisher left Florida State for Texas A&M, Florida State hired Willie Taggart from Oregon to replace Jimbo; and separately, Florida hired Dan Mullen away from Mississippi State.