(There’s a funny aside on Thermopylae, and the limits of ‘excellent leadership,’ yes they did well but they ultimately lost. To which I would respond, they only ultimately lost because they got outflanked, but also in this case ‘good leadership’ involves a much bigger edge. A better example is, classically, Cortes, who they mention later. Who had to fight off another Spanish force and then still won. But hey.)
I know this is an aside to your aside, but as an avid Sparta-hater, I want to point out that we don’t have much evidence that Spartans are good at military leadership, and indeed plenty of evidence in the other direction:
Sparta’s opponents often won using clever, innovative tactics, such as at the Battle of Phyle (404 BC), the Battle of Olpae (426 BC), the Battle of Cyzicus (410 BC), the Battle of Arginusae (406 BC), Battle of Tegyra (375 BC), the Battle of Leuctra (371 BC), and the 2nd Battle of Mantinea (362 BC). The Spartans, so far as I have found in reviewing these 51 battles, never made a single creative strategic or tactical innovation. They were sometimes clever; mostly through treachery and trickery.
That said, you have to remember that pretty much all of the primary sources you read on this topic are written by Athenians for Athenians, and less about preserving an accurate historical record for future generations (or even propaganda/promoting internal Athenian solidarity) and more about making specific political points for their own internecine fights. So you should pay more attention to what’s objectively verifiable (things like win-loss records, inputs and outputs) and less about the overall vibe that they present.
I know this is an aside to your aside, but as an avid Sparta-hater, I want to point out that we don’t have much evidence that Spartans are good at military leadership, and indeed plenty of evidence in the other direction:
That said, you have to remember that pretty much all of the primary sources you read on this topic are written by Athenians for Athenians, and less about preserving an accurate historical record for future generations (or even propaganda/promoting internal Athenian solidarity) and more about making specific political points for their own internecine fights. So you should pay more attention to what’s objectively verifiable (things like win-loss records, inputs and outputs) and less about the overall vibe that they present.