are accurate. It also didn't hurt that the Big 8/Big 12 played games closer to Texas with more frequency.
In order (in my mind):
Didn't want to follow his brother
John Walsh was the starter
Paul Shoemaker - even though due to a mission he didn't "play" until 97, year after Koy graduated
Non-LDS (His parents never really liked Ty joining)
Conference (Colorado wasn't a better program, very similar levels)
While Koy played all 4 years, he was only the full time starter his senior year.