This is the question. I think there are two reasons.

Five star players have been told for a long time that they are special, the best of the best. They have been told that they are NFL bound before they get to college and so that becomes their priority. With that in mind my hunch is that some are just not that interested in the academic side of college and don't want it to interfere with the pursuit of glory on the gridiron. The second reason, and probably more important one, is that the top guys get a lot of advice from people in the know, and they all know that Kelly is not a top flight coach. He is not going to achieve what they want for themselves or their team. These players want the best coaching they can get, and they can't get it with Kelly. They also want to play for a coach that NFL people can rely on to coach them well and to be honest about the player's abilities. Once we replace Kelly with an elite level coach the 5 star players will return to ND.