Nero was actually outside of Rome when the fire started, but rumors of him 'fiddling' while Rome burned quickly spread amongst his opponents. The official story Nero's government went with blamed the fire on Christians and began persecuting them.

In terms of benefits, though, in the aftermath of the fire Nero was able to redesign the city with a more organized street grid that improved cleanliness, open space, and the quality of life for the poor. He was also able to begin construction of his palace, the "Domus Aurea"(House of Gold). While he did take tangible benefits from the fire, their is no evidence that he actually started it himself.