Why is classical education so much more fascinated with the sacking of Rome over the collapse of the Republic? The latter is, to me, far more fascinating and far less explored in our common curricula.
> If a civilization could descend from Cicero and Cato to Caligula and Nero in scarcely a century, how long could the brave experiment launched by Madison, Jefferson, and company hope to endure?
This describes the fall of the republic, not the fall of Rome half a millennium later. Nero and Caligula are among the first emperors, not the last.
Unintentionally, perhaps. Really, this is an indication of the article's incoherence and sloppiness. It purports to be mostly about the aftermath of the collapse of the Western Empire in the 5th Century, and how this supposedly cleared the way for assorted awesome developments (five or six hundred years later). So the transition from Republic to Empire is irrelevant to the argument.
I think part of it is that the end of the republic is so well documented, and that documentation so thoroughly studied and responded to up through the 19th century that it's hard to come up with anything really new to say.
The period immediately after the fall of the empire has precious few surviving contemporary accounts. Much is known only through archaeology or very fanciful writers like Isidore of Seville, and so there is a blank canvas to project one's hopes and fears.