Why do fans support teams?
Is it because they come from the same area/country? Sometimes. Mostly. Is it because they like their style of play? Might be. But the main reason why? It's obvious. Winning. Being a champion. Constantly.
A lot people forget this sometimes. You see people raging about other people who are suddenly Chelsea fans, and Manchester City fans and Borrussia Dortmund fans, etc. But it's not that hard to understand.
They like them, because they win. If Manchester United and Barcelona (two sets of fans who have the most to say about everything) started losing and started to become midtable teams, they'd retain many of their fans base, the die-hards, but they will also lose many, many fans!
I can think of a few teams, like Valencia or Liverpool, that used to be very good and won things during repective periods, but that has since tapered off and they've become less a champion and more a has-been relying on history to boast. They still have many, many fans and are still quality teams, but the glory-hunting fans have long sinced moved on, but I dont blame them.
Before I really watched football and before I truly understood the game and its dynamics, I, too, was a glory-hunter and a fence-sitter, I didnt really take note of who played and cheered on the best/winning team, but after witnessing the miracle that went down in Istanbul in 2005 I made the decision to watch soccer, as a fan, and decided to support Liverpool. At that time, was I a glory hunter? Yes. But after learning more about the club, their ethos, what it stands for and it's illustrious history, I am forever a red. We walk on no matter how inconsistent we are.
The same thing might have happened to fans watching how Chelsea won the UCL last season in such a hard-earned manner, or City that thrilled the world with their last-gasp snatch of the Premier League last time out. Moments like that can create or forever turn a fan to support another team, not because the person is necessarily a glory-hunter/fence-sitter, but because us as humans respond to champions and winning. It's simple really.
The same thing can be seen in history and legend in stories like David and Goliath, the legend of Spartacus, the Springboks in '95. People love an underdog winning and they love it when they become Champions.
So next time you feel like raging about fence-sitters just remember that to each his own, and that champions are usually who pulls the fans. Nobody really cares about second place.