I asked something similar back in 2001. Good to see some things never change, I guess. 
The best answer came from Juniper200:
Why are the Lions so bad?
It’s been a long-standing style of management. I hate to pick on the Ford family, but they run the team like they run their company. Vocal types have always been pushed out for pennies on the dollar.
We REALLY needed continuity. I wanted to see a stable coaching staff, even if they may or may not suck, together for 5 years. I’d also like to see an offensive line together as a unit for a couple years as well.
I really need to become independently wealthy and buy this team. I’m dead serious.