Overrated: What a Joke!

The chant you commonly here when lower ranked program pulls out a big win over a higher ranked program is "Overrated...Overrated...Overrated..." Now can someone explain this to me? I see this chant as taking away from the big win your team has just pulled out. I mean if a team is overrated then your win does not mean as much. What I am trying to say is congratulate your own team don’t attack the other team after a big win!