Watching people watch football is like watching a competitive sport of its own.
A kind of histrionical show-down of who can be the most obnoxious;
Who can really drive home the fact that they want this particular group of color-coded men to win more than the other,
with egregious displays of enthusiasm being the most popular mode.

In a parallel world, some of these folks could make decent actors.

My brother, for instance, reminds me of a young Leo:
He yells and shouts but never quite manages to sell me on it.

My uncle's more like a Michael Caine. Calmly sharing reassuring statistics and factoids throughout the game.

Meanwhile, my father's much more stoic. If he has any real interest in who's winning, he doesn't show it.

I've seen this behavior on display in other venues
(the workplace, concerts, church,)
but it definitely seems to be the most pronounced with sports.