Rob Ryan "Perfect Fit" comes from Belichick/Parcells tree

I think most of the prejudice against Ryan is with his ties to Buddy Ryan's (by blood) bounty habits. He has never had the type of team structure or offense that the Saints will offer. Dallas had a good defense, and Romo being terrible created a lot of short fields for the defense to defend.

On a personal note, I am not for or against Rob Ryan. It makes a lot of sense for the coaching staff (and Loomis) to do their due diligence in finding and hiring the best man for the job.