Reinabas comes from the verb reinar, meaning 'to reign' or 'to rule'. It's a regal and evocative word that isn't commonly found in everyday song lyrics.
In
"Te Vas" is a breakup song that doesn't rage, it just lists what it's about to lose. The narrator runs through the small stuff a relationship is actually built on: "Quién te despertará, Con un beso por las mañanas" (Who will wake you up, With a kiss in the mornings), "Dime quién te llevará, El desayuno a la cama" (Tell me who will bring you, Breakfast in bed). None of it is dramatic, and that is the point. He isn't fighting to keep her. He's cataloguing the ordinary mornings someone else is about to inherit.
The chorus admits the part that actually hurts: "Pero sé que por algo, Quizá con él me has de comparar" (But I know that for some reason, Maybe you'll compare me to him). He doesn't argue his case. "No creo ser mejor, Fui diferente y nada más" (I don't think I'm better, I was just different, nothing more). He has already lost the comparison in his own head before she's made it. It's a cumbia built for dancing, but underneath it is just a guy watching someone walk out the door and refusing to pretend he had the upper hand.