including myself, and more money, more opportunities, new challenges, more resources, new heights to scale, etc, is pretty common. Its the case for many CBers and its the case for most athletes and coaches. Its the rare, rare exception that a Lavell type person stays at a school for decades.
I dont think its just greed as you allege - it certainly can be greed but I think that there are lots of other reasons that driven, competitive people move to new challenges as they chase dreams and goals.
IMO with Pope, even if it was the same amount of money that UK was paying him as what he was getting at BYU he would have jumped for that job, wouldnt you think?