Look at the way Lucas looks at Peyton vs how he looks at Brooke. I mean it was clear as a day who he was in love with. And the way Brooke looked at Lucas while he was staring at Peyton says it ALL she KNEW that he loved Peyton...
LOL They did it for dramatic effect and the song helps out with that. Take away the song and you have a hilariously long and awkward moment of epic proportions lol.