Fisher's teams had Steve McNair from 1995-2005. When McNair started, the team was 76-55 (58%). When McNair did not start: 20-25 (44%).
He had Vince Young from 2006-2010. When Young started, the team record was 30-17 (64%). When Young did not start: 15-18 (45%).
Not coincidentally, a 44%-45% win percentage yields.... 7-9.
Fisher rose through the ranks because of his affiliation with and endorsement of Buddy Ryan. In his position coach and coordinator roles, his groups produced. Guys stick around for so long because of familiarity and hope. And management's fear that the next guy might be worse.
That said, middling coaches could have gotten similar results with the personnel he had. Here's a random selection of some of the players he had on his winningest teams:
1999 (13-3) - McNair, Jevon Kearse (1st round pick),Matthews, Wycheck, George, Rolle, Bishop, Mason
2000 (13-3) - Everyone above, add Keith Bulluck (1st rd pick).
2002 (11-5) - Similar to 2000, add Kevin Carter in 2001, Albert Haynesworth (1st rd pick)
2003 (12-4) - similar to 2002. (note the DL, like in 2002, contained Kearse, Carter, and Haynesworth)
2007 (10-6) - Young, Vandenbosch, Haynesworth, Mawae, Bulluck, Mike Griffin (1st rd pick)
2008 (13-3) - Chris Johnson (1st rd pick), Young, Kerry Collins, Griffin, Mawae, Haynesworth, etc.
2008 was the year Young got hurt and Fisher decided to stick with Collins. They finished 13-3, which helped Fisher convince himself that he was the reason (not the players). Note that the above 15-18 "When Young did not start" includes the magical 12-3 from Kerry Collins.
I typed all of that to say, "F Jeff Fisher."