Work relationships matter. Rosters can be turned over. Cap can be fixed. But jobs where the HC is the clear Alpha in the building and the owner/organization are committed to winning is rare.
Vrable didn't work in Tenn because of GM/owner. Jets imploded because of owner had to fire HC. Carolina QB Young was drafted by owner and HC fired after 1 yr. Jags GM runs it. Raiders - enough said. Saints job is probably the 3rd/4th best behind the Pats, Bears, and maybe Dallas.