Max Kellerman breaks it down so
This team is the most covered, and players are well known.... but they simply aren't as talented as people make them out to be.
Lawrence was drafted to replace DWare and has never lived up to that.
If you look at the players who end up leaving Dallas, they normally don't do well with other teams. And the ones that do, speaks to the fact that the GM doesn't know how to properly evaluate people.
Taco had talent and he probably left because the cowboys are covered so much and because staying there and not playing and getting criticized was going to hurt his long term reputation with teams.
Dallas getting so much coverage and so many prime time games is really a curse.