Other then Belicheck, who had a frustrating, difficult run as Browns HC from 1991-95 but also had to contend with a meddling, egotistical, egocentric owner in Art Modell who was needlessly spending money he didnt really have and had to use his wife's banking account once to sign Andre Rison as a FA early in the 1995 season, the other HC's you mentioned had outstanding careers or tenures as coordinators elsewhere. Bill Walsh couldve gotten a HC gig a lot sooner then in 1979 if Bengals owner and HC Paul Brown hadn't secretly bashed him for years behind his back, telling other NFL teams' owners and GM's that he was emotionally, mentally unstable and could not handle the stress and responsibilities of being an NFL HC.