Note how Tacitus’ tortuous syntax here seems to underline and suggest the progress of the fire. The confusion is similarly echoed in the human reactions of the following passage.

Given the preceding description, any Roman reader would draw an obvious conclusion, viz. that the fire was a divine punishment.

Given Thrasea’s beliefs, the whole paragraph could be a subtle reminder of that Republican libertas which had been lost; note the use of three different words for law.

You may know the excellent Nero episode (from the BBC series ‘Rome: The Rise and Fall of an Empire), which begins with the aftermath of the fire.