Coordinator Prestige

So I am doing a FSU Dynasty where I don't play, I just recruit, make subs, do lineups, hire coaches, you know, basically everything but plays kind of like the CEO role in real life. I hired an A+ former HC as my OC, and I went 16-0 with a Natty his first year, then the next year I went 14-1 lost on the semis to the eventual champions. I said all that to say, my coordinator went from A+ prestige to a C+ prestige in ONLY 2 years despite winning a Natty in an undefeated season, 2 straight conference title wins, and only one loss in 2 years. He is a C+ prestige in the current 3rd year. Why is it that with all that success his prestige dropped from A+ to C+? Does anyone know, because my DC started with B- prestige and went up all the way to an A- prestige? If anyone knows why just tell me