Why are Newcastle so crap?

I always wonder why they are so crap, they have all the money they want, but still can't get a decent side together. They seem to have a team of has beens or younger players tipped for success but never achieve a lot, what makes them a poor club, do you think players just go there for the money and don't really care about playing for a successful team or do you think they do things to please the fans that have a negative effect on the club (like Keegan)?