When I was a student, and a lot later to be honest, I was taught to be a bit sniffy about Suetonius, biographer of the Twelve Caesars. This was the gossip of the Roman empire. Suetonius may have had good access to the stories of the imperial court behind the scenes (he had worked in the proto-civil service in the Roman palace, and so had privileged access to the imperial filing cabinets, and quoted a few choice documents in his biographies). But he was a 'biographer' rather than a 'historian', and so a lot lower down the intellectual pecking order. And we looked askance at the stories of what Tiberius got up to in his swimming pool (little boys nibbling his genitals, according to Suetonius), or Caligula's plans (only plans, remember) to make his horse a consul.
It took me a good few decades to see that there was a lot more in Suetonius. And that came when I decided to read not just individual lives amongst the Twelve (according to which emperor happened to interest me at the time), but to read the Twelve Ceasrs, sequentially, cover to cover -- as I imagine they were originally intended to be read. When you do that, you see that Suetonius offers more than you might have thought. He isn't giving you just twelve individual biographies, but a story of dynastic succession and the transmission of power.
Hence all the stuff that Renaissance artists were smarter at picking up than we are about omens of rise to the throne, about the complexities of the transmission of power. It may be that we have got preoccupied by the anecdotes of transgression, but that's partly because we have skipped over all those portents and omens about imperial succession (the eagle landing on Claudius' shoulder, the dead man's hand presented to Vespasian, and so on).
But there are also some individual passages of Suetonius which hit home much harder than we often acknowledge.