Se esfumó comes from the verb esfumarse, which means "to vanish" or "to disappear into thin air," much like smoke (fumo). It's a beautiful and slightly dramatic word you won't hear every day.
In the song, the artist sings "Todo lo que fuimos se esfumó de aquí" (Everything we were vanished from here). He uses this word to powerfully describe how the entire relationship and all its memories simply disappeared, leaving an empty space behind. It perfectly captures that sudden and complete feeling of loss after a breakup.
This song from Spanish artist Íñigo Quintero is a deep dive into the confusion that comes after a breakup. The singer is completely stuck, realizing that his whole world was built around one person. He sings, "Porque yo he tardado tanto en olvidarte / Me he dado cuenta de que todo era amarte" (Because it has taken me so long to forget you / I've realized that everything was loving you). He feels like he can't be happy anymore and doesn't know who to blame for the pain, asking if it's his fault or hers.
But there's a twist that makes it all so much more complicated. It seems the ex came back at some point, crying. The singer is left asking, "Di ¿por qué volviste a mí / Si yo no era nada para ti?" (Tell me why you came back to me / If I was nothing to you?). This question hangs over the whole song, mixing his sadness with a real sense of frustration. He just wants to be the owner of his own time and think about himself, but he can't seem to escape the memory of this relationship.