We regressed, because that was the standard pattern for every aging dynasty. We regressed because we had salary cap issues because of the back-loaded contracts that won as all the previous Super Bowls. By the time BP came into town, everything was set for the DC organization to make the moves needed to become a major player in the league again.
Everybody seems to avoid this basic question. What happened to the other dynasties before Dallas' reign or even during Dallas reign after their run? This question also needs to be seen in the context of the statements of Bill Walsh, who pretty much states the modern day version of free agency was implemented because the league saw Dallas running off a major string of Super Bowls. This essentially means that free agency pretty much targetted the Dallas Cowboys, so what do you expect?
Playoff contenders how? Two of the 4 seasons, we didn't even sniff the playoffs. If you have high draft picks, no salary cap issues, and a big hand in the organization, coupled with an absolutely horrid NFC East, you better turn the organization around, because there really is only one way to go.