Been here a while and never saw this with any of my teams. I was qualified for like 2 C schools in Knight.  Wanted to get the highest possible job this  season.
So I applied and got Arkansas Pine Bluff. 
First time I checked, I see the prestige dropped from C to C-.
Why would hiring me make it go down? I got A+ in everything and my record is spotless. 

WTF???

This is normal. I think almost every new team I've taken over has experienced a 1/3 grade drop in prestige. If you have only seen it happen once, perhaps the drop is only a small fraction and not enough to be visible in most cases. 

I would be curious to hear from others WHY this happens though. 

When I went from Wingate (D2) to St. Louis the prestige actually went up from D+ to C-

I don't know about D1, but in the lower divisions, a school with a new coach almost always drops in prestige. There was one DII team that had won 13 NT games in 4 seasons (RU, Final Four, Elite Eight) and dropped from A+ to A when it got a new coach. When I questioned it, WIS confirmed that the drop was due to the new coach but  the school was very close to maintaining the A+ regardless.

yeah, i once lost my team (due to forgetting to buy a season), signed up for it again, and had a 1/3 grade loss. same ID, same record, blah blah blah.

ah ok. still really dumb, though C- and C is a difference at D1.
oh well.