I live 2 hours from KC. I'm a Royals fan. I've watched the team flounder without leadership for fifteen years.
One magical season (or rather month and a half) doesn't bring back fans in the numbers the team's standing may dictate.
In my opinion, Kansas City is a football town and St. Louis is a baseball town. Nonetheless, if ownership continues to push the improvement of the team, the K will be full again.
When people are jerked around year after year, it takes awhile for them to come back!
It isn't entirely the small market problem--it's the sense of floundering with no plan and no hope that really drives away fans. Also, during those years, the Royals have lost radio stations to the Cardinals and probably to other competing teams, so the great area around their base is no longer automatically drawn to KC for a game.
Bottom line: put a team on the field and people will come. Have a lousy team, and all the gimmicks in the world won't bring fans in.
As Mike implies, football is more of a happening--an excuse for a party in a time of year when there isn't much else to do. Why else would so many people gather around a tv set to watch fat men run into each other, punctuated by inane patter by even older fat men!
Dave N