Difference: FSU's use of the name and image (by the way... it's a "nickname", not a mascot... THAT would be disrespectful) is approved by the Seminole Tribe of Florida (and has been since FSU agreed in 1972 to implement more respectful traditions and representations). The NCAA listed it as one of the schools using "hostile" nicknames until 2005, when,with the Seminole Tribe of Florida already approving of the name, the Seminole Nation of Oklahoma's General Council voted to revoke the tribe's public opposition to the use.
Had UND's use of the Fighting Sioux been approved by both remaining Sioux tribes (Standing Rock and Spirit Lake, they did get the approval from the latter, but not the Standing Rock tribe), then the NCAA would have dropped their case against UND.
FSU's use of the name and image is approved by the affected people, UND's is not. How is that difference "unfathomable"?
(Can you tell I'm an FSU fan?)