I feel Pruitt selected his staff well when he got here. But he changed both coordinators this year, so it is not all his "original" hires. Turnover happens when you do extremely well. Other schools fire staffs every year, and offers are made. Since the bowl game hasn't been played yet, if any of our current staff has offers, it is hush hush for now.
As to Fulmer's decline, it was more a decline in recruiting, and not having Cutcliffe to handle the offense. Even greater, IMO, was a poor focus on discipline. He had a rash of player's arrested, and his way of dealing with it, per an interview I heard at the time was, "The players have my phone number." All that put together, and the failure of the Dave Clawson offense after Cut left for Duke, led to Fulmer being fired. And the only person I have heard blame a lack of stability of the staff? That is Fulmer himself.
Edit: I tried to link a 2008 article from bleacher report, but after 2 attempts, it fails to load. Guess that article is not allowed to be posted. So google Phil Fulmer fired. It will show up.