It’s so large and out of control that I have to wonder if it wasn’t deliberately set.
Bad wiring and no sprinklers prossibly.
Of course if it was torched, then it may have been to conceal a heist.
I know..burning throughout in an even way. At least it appears that way.
Brazil is in financial crisis. Arson to cover up illegally sold precious items would not be out of the question. Also, museums have insurance.