Philosophy

Divine mania seems to much more limited in scope than I had initially thought. At best, maybe it’s tangential to concepts within Apollonian and Dionysian aspects.

From a Platonic perspective I'd say it's the other way around,that Nietzsche's absolute distinction between the Apollonian and Dionysian is tangential to the providence of the Gods.

As I mentioned there's something of a false dichotomy that's to my mind somewhat ahistoric when looking at Nietzsche's Apollonian vs Dionysian. For Plato and the Platonists that follow him up to the 7th Century CE the Gods are not symbols that can be reduced into frameworks but instead are the causes of all things.

For Plato, Apollo and Dionysus aren't frameworks to look at life but particular Gods, worthy of piety and devotion. There's actually a lot of Dionysian themes in Plato but not in our modern Nietzschian framework eg but from Plato's context as a devout Polytheist influenced by the religion around him and Orphic Mysteries. As Plato himself says in the Phaedo

"The thrysus bearers are many; the mystics few".

I’ve had a little trouble believing there are 4 sources, given prophetic and ecstatic were both likely drug induced, ethylene gas poisoning and drunkenness.

There are 4 sources types of Mania that were mentioned, but remember in the Phaedrus the main theme is how Erotic Mania (specifically a kind of homoerotic mania at that) elevates the Soul to its leader God and the banquet of the Gods.

So for Plato, as an Idealist and Polytheist wouldn't accept the physical causes of these things you mention but instead find the causes in the Gods (see Timaeus).

This is something the later Platonists continue. Proclus, in the Platonic Theology (Book I, Chapter 24), writes that

As therefore through the first goodness all the Gods are boniform, and through intelligible wisdom they have a knowledge ineffable, and established above intellect, thus also, I think, through the summit of beauty, every thing divine is lovely. For from thence all the Gods derive beauty, and being filled with it, fill the natures posterior to themselves, exciting all things, agitating them with Bacchic fury about the love of themselves, and pouring supernally on all things the divine effluxion of beauty.

So here the Dionysian mania, the Bacchic fury, is the Providence of the Gods which overflows into all of reality and fills us with a love of the Gods through the Goodness and beauty of the Gods, an overflowing providence which causes reality to exist. In this light the 4 manias specifically mentioned become the providence of 4 particular Gods emanating their Providence in individual ways - so while these are the four kinds worth mentioning for Plato, as being the most visible examples in Greek Polytheism and culture of how divine mania impacts us, aren't necessarily the only forms.

I think you're right to say Plato didn't invent these manias, 100%.

Instead Plato is describing things he sees around him which he thinks are caused by the Gods. The Oracles of the Gods and the impact of initiation into the Mysteries and the power of poetry and Eros are well known by Plato to be a) not rational but also b) facts of reality for him which c) are of divine origin.