Parkinson's schematic is ridiculously, well, schematic. And from this perspective in time, the usual ideologue's move of taking a concern of his time (anti-liberalism and big government) and claiming it applies over all time.

Democracies die because of too much welfare? Ridiculous! Is that how the Athenian democracy died, voting too much pay for jurors? Is that how Weimar Germany became Nazi Germany, because the burgomasters were drawing too much disability? Is that how the nascent Japanese Meiji democracy was snuffed into militarism with the Emperor's aid? Is that why Sun Yat-sen's democratic movement split into the Communist and the corrupt KMT, because they were voting themselves largesse? Venice's oligarchical democracy didn't seem to have any such problem before its conquest. And so on.

The monarchy to democracy progression is little better. I bet you could not name 6 clear examples of that, from the full sweep of human history. Certainly it doesn't apply to America, Japan, or Athens, which either went straight from aristocracy (such as it was) to democracy, or retained the aristocracy well into their democratic periods.

(I used to think my time reading people like Thucydides or Herodotus or Gibbons was wasted on trivia, but at least it saves me from grotesquely false simplifications.)