That was the first time in history that all of the medalists in the M 1500 came through the NCAA system Hocker (Oregon), Kerr (New Mexico), and Neguse (Notre Dame). They have a combined 8 NCAA titles.
This century the closest was 2016 when two medalists went through the NCAA (Centro and Willis) and every other year this century had 1 medalist in from the NCAA (Lagat '00, '04, Willis '08, Manzano '12, Kerr '20)...
Does anyone know when the last time this happened in any distance event (men's or women's) at the Olympics?