It happens every year, some years bigger jobs open up over other years.
The top three jobs this year were the Arkansas, Stanford and Wisconsin jobs. Arkansas' McDonnell retired. Arkansas filled their position quickly with the Northern Iowa coach, who was replaced by one of his assistants.
Stanford filled their vacancy with the UVA coach after Tegen retired.
Wisconsin lost Schumacher to Nike, who is paying him nearly double the salary he earned at Wisco. Wisco hired Iona's coach.
This happens every year. There are 20-25 top distance positions that hundreds of coaches apply for. Then it starts an ongoing rotation of coaches when one coach takes over a major program, he leaves a job open at another school. It all comes down to more money, better resources and a large recruiting budget.