You don't really believe this do you? I've seen way too many coaches that just aren't very good get moved from one team to the next because they hit the jackpot once. Going back the first one to mind is "We punted on third down to surprise them" Rich Kotite and more recently "I can force my college style offense into the Pros" Chip Kelly. Then there are the perennial losers like Lewis producing sub-500 seasons for close to half their tenure with a team.
I guess if you mean "best man" you're including how the person interacts with players, other coaches, management and ownership maybe, or if it's more reflective of "best man" available.
To me far too many NFL owners/GM select HC on criteria that has less to do with performance than feels.