Quote:he's also reporting that the Romans suspected Nero of starting it. Why?
Why? Why indeed? There are some people in history who we know only through the writings of their enemies. Nero is one of these. Caligula and Herod the Great come to mind as two more examples. Even Hitler does not suffer from this particular problem.
Tacitus was a member of the senatorial class. He himself also noted that he owed his career to the Flavian Dynasty ( Vespasian, Titus, Domitian) and it was the Flavians who picked up the pieces of the empire after Nero fell. All sorts of slanders are written about him by writers who came after the fact and belonged to the upper (and literate ) classes.
It is impossible to comprehend Roman history - particularly Roman political history - without understanding the centuries long battle between the patricians and plebians for power. G. Julius Caesar represented the triumph of the popular party over the senatorial class.
He founded the Julio-Claudian dynasty of which Nero was the last member. If there is one thing the Julio-Claudians understood it was that their power was based on keeping "the mob" quiet. There were no popular uprisings against even Caligula or Nero. Their opposition came from the senatorial/equestrian classes and generally had to do with the rather innovative ( read that 'extra-legal') means of extracting money from the upper classes. When the revolts came against Nero they came from Vindex in Gaul and Galba in Spain...the governors of those provinces.
So who was Nero? Even Tacitus' account indicates that Nero took steps to relieve the suffering of the poor and his own palace was destroyed in the fire. It is also true that in the aftermath of the fire he built a new palace for himself, the Domus Aurea, which was opulent beyond words ( sections of it have been found and excavated) and he no doubt financed it by extorting money from the upper classes.
What is the reality of Nero? Who knows. Did he extort money from the upper classes? Doubtlessly. As Willie Sutton noted "I rob banks because that is where the money is." Did he incur the enmity of the upper classes as a result? Obviously he did.
So in Tacitus' (and Suetonius') case we have a double motive for what they wrote. Class warfare and a desire to ingratiate themselves with the current government by pointing out the flaws of a despised enemy. We lack a favorable biography of Nero and, much as with political advertisements today, the negative ones must be taken with caution.