http://www.post-gazette.com/pg/07035/759363-66.stm

Although his legacy was strong, Tagliabue didn't get past the first round of voting by the panel of 40 media members. The former NFL chief oversaw labor peace throughout his tenure; helped enhance diversity in coaching and front-office hirings; negotiated television deals that bring in more than $25 billion; led expansion from 28 to 32 teams; established the NFL Network; and guided a rising global presence.
That link talks about the other players that got in; but how in the world does a Commissioner who followed in the footsteps of the great Pete Rozelle not get in on the first ballot in the wake of so much that's done for the league ????