It’s just incredible that there are still records that exist that can be used to tell this story.
It is a mark of the so-called "middle ages" or "dark ages" to have periods in which reporting falls...
So yeah I'm amazed too -- this stuff survives.
(The original poster wrote «records that exist that can be used to tell this story»: of all the documentation that can be lost, that produced during the first imperial Rome is probably some of the most secured. We still lost a lot: for example, the culmination of that period is probably under Trajan, and he wrote the Commentarii de bellis Dacicis - lost, contrary to its model, Julius Caesar's Commentarii de Bello Gallico...)
Without that -- they become lost.