As a football (read— soccer) non fanatic whatsoever, this change in behavior that happened personally to me while watching the Champions League Finale had been unusual, to say the least.
Cheering up for one’s favorite team can become, as it is widely known, an intense, almost religious-like practice. Thousands of fans gather up, sing anthems, cry at defeats, curse the opponents, and bang their fists on the table. During the viewing of a game, especially in social outdoors contexts, I’ve seen fans express the most fervent feelings: biting nails from the stress they undergo, shed tears of happiness or sadness (as the case requires it), and all in all— these people get deeply invested in every single one of their teams’ games.
What happens here seems to be not only the simple herd behavior, according to which in large crowds of people individuals act and behave according to similar models, even without a central authority. There is a whole field of studying sports fanaticism which brings together elements from sociology, psychology and physiology.
This “social experiment” I underwent while watching the game reinforced the psychological and sociological connections to what sports fans experience. Even without having a previous preference for one team or another, I somehow got myself drawn into the cheering-cursing-bang-fist-on-the-table behavior. And it was fulfilling.
Most of the fans I’m quite sure are not connecting this kind of behavior to deeper rationales. Loving one team and hating another is put in sociology in terms of “ingroup/outgroup”, or identifying and belonging as being a member from one group vs. not belonging and rejecting the other considered rival. And to the level to which this identification goes is much larger.
Some say there are clear psychological benefits from identifying with a sports team, such as “higher self-esteem, they are less depressed, less alienated and less-lonely”. It is all about being part of a group, identification, community and feeling of connectedness.