Absolute power means abject poverty
This index is in de facto a measure of centralized power. If you notice the most economically viable countries are generally those with decentralized power. Their politics and societies are generally free of intimidation. (the U.S. tied at 12th with Switzerland) Those with the most centralized economies and repressive regimes are generally the poorest countries.
Even though the article doesn’t make the connection, the really important variable is Power. The more it is checked and held accountable, the better the economy. No surprises here. Power is something that matters across the spectrum of a country: concentrations of Power matter in politics, economics, society, the legal system, education, religion, sports—everything! If Power is minimal, then People prosper and thrive. If Power is concentrated, then People do the bidding of others—not themselves—and they do not prosper. And if Power is concentrated everywhere, we find totalitarianism, which is most simply defined as a political system which tries to control everything, including thought. And in such systems, power not only kills, it impoverishes.