It is religious literature, and it was sent to comfort/warn the Christians Nero was slaughtering.
Revelation 1:1 — “The Revelation of Jesus Christ, which God gave to Him, to show to His servants things which must shortly come to pass...”
The Lord really missed a good chance to say: “to show His servants things which will occur thousands of years in the future.”
Rev. 1:3 — “...for the time is at hand.”
Rev. 22:6 -7 “”And he said to me, These things are faithful and true: and the Lord God of the holy prophets sent His angel to show to His servants the things which must shortly be done. Behold, I come quickly...
Mat.: 10;23 — For assuredly, I say to you, you will not have gone through the cities of Israel before the Son of Man comes.”
There is no corroboration in the secular record of any systematic Christian persecution in the 1st. C. It didn't happen.