Maybe, but wasnt this supposed to be somewhat gradual? Instead of an overnight plunge?
Consider that GRU is Brazil's largest airport, and BSB is Brazil's largest hub for both of its 2 largest airlines (i suppose the data takes this into account). Even if BSB wasnt a hub, its still one of the largest airports in the country, its the federal capital after all, so i'm inclined to think this sudden dip in demand is some kind of bug
EDIT: Extra info
THIS WAS PROBABLY A ****ING JOKE