I think you hit many of the key points. I think first and foremost, performance on the field is a big reason why NU ends up as #2 on a recruits list rather than #1. When you play a team like OSU in a nationally televised game under the lights with a lot of visibility (it was a top-10 matchup at the time), and demonstrate complete incompetence in all aspects of the game in a 59-point loss, it does more than just add one loss to the W/L column. It sends shockwaves to any recruit looking at Nebraska and creates a gap of just how far behind NU is with the top teams in football. I would rather NU have finished the season 7-5 or 8-4 and kept all games close than end at 9-3 and have two games where the team was obliterated.
The other key point is that track record of the head coach. Riley is working his butt off to change the momentum and culture around recruiting, but his long career as a coach can also be a detriment when he has basically been mediocre any place he has gone. Recruits want to play for winners, and Saban, Meyer, and Harbaugh have proven they can win with multiple programs. A recruit like Tyjon Lindsey would rather play for a team whose head coach is a Jack*ss and whose position coach is inferior to NU's WR coach because the head coach has won every place he has gone.