Milton Friedman said once that good theories are those that provide correct and useful predictions. And he certainly went beyond of duty to make sure his predictions would become reality.
The big problem with economics is that it is not a science. It is ideology, like all political philosophy, and that enrages economists. Actually, economics doesn't even exist as a stand alone discipline in its own right. Take Adam Smith, for example. The poor man brought economics into being when he spoke of that magical land of barter, even though it has been anthropologically debunked that such a land ever existed. But that myth was "needed" because it implies that, before governments existed and money and credit were used, humans were already situated in a market --which gave economists an actual thing to study.
However, the spontaneous combustion of economics wasn't complete , because those snake oil peddlers needed now to severe their imagined discipline from the other social sciences, and so they pulled out of their ass the pathetically reductionist ethics of Bentham, for whom humans were hedonistic automata, i.e. unidimensional, selfish fuckers concerned solely with procuring pleasure for themselves and avoiding pain at all costs. The obvious truth is that humans are damn complex and everything they do is irrationally connected to their desires, societies, upbringing, and whatnot. But recognizing that would not allow those little freaks to steal mechanics and maths to create the illusion of a human measurable like pebbles on a beach, and, henceforth, susceptible of being forced into little, reductionist and silly models.
One last thing was needed for the fraudulent quacks to become respectable "scientists", though, and that was to simplify even more their astrology-like field so they could create their little, incomprehensible, ivory tower alchemy laboratory. Enter methodological individualism. This is merely the quasi-religious belief that only one thing matters and that is the individual, to hell with classes, groups, institutions, or societies as a whole. In order to do their little equations, the despicable hacks needed to simplify even more, so calculations could be done with charts and curves and, from there, claim that they understand the world using coins and thus predict what's going to happen.
So, as you can see, these bastards took a super complex matter (human societies) and dumbed it down so they could use classical mechanical theory ("equilibrium" rings a bell?), and kick history, sociology, and many other necessary subjects out of their cool boys club. If the drama had stopped there then all would be cool, but since these shamans of fakery are not scientists, their political instinct kicks in all the time and what is claimed to be a descriptive discipline leaks all the time into a normative one. Hence you see these hacks all the time saying what "should" be done and they use as a basis their unrealistically simplistic and erroneous models. Since those with the cash benefit a LOT from such quackery, they always splash resources on selling the debunked theories of these glorified accountants, and then roll the tanks over any society which refuses to crack open to their greed. That's why the world has been screwed.
This is when Milton Friedman enters the scene. This little fucker pretended that his models were real and sold the idea that whomever wouldn't swallow them was against the logic of his bulletproof "science". In those days Latin America was already the favorite laboratory of these astrologers and, since their gibberish caused new markets and delicious raw materials to be at the disposal of multinationals, they were very well funded. As a cherry on top of this shitcake, the CIA was very happy to aid in the spreading of the neoclassical gospel.
And so they did. Chileans, who are swimming in valuable copper, elected a left leaning man who was bad news in the board rooms of the multinationals. Furthermore, he wanted for Chileans to be the owners of their resources, and for his people to be protected from the rapacity of the colonizing powers. Friedman wasn't going to allow that and he wasn't alone in his outrage. How come someone dared to do well with a different model than his? Corporations weren't happy and the CIA, of course, was there to serve the interest of its maters. So they all meddled into Chilean politics like a Russian hacker getting an orange man elected to the White House, and after bombing the shit out of the Chileans they put in his place a thug who would happily implement the "right school" of economics.
Yeah, look at this little rat and his thug puppet.
So, at the end, the predictions were correct. A lot of investment came into Chile and the GDP went up, no matter how many Chileans were assassinated and silenced during decades. Who gives a shit about democracy and the right of peoples to self-determination, right? What matters is that a prediction is correct and to hell with anyone who stands in the way between reality and a good supply and demand chart. Right?
Next, I'll give my readers a crash course on Marxist economics, so you see that no matter what ideology the quacks espouse they always end up shitting on everyone and causing a lot of deaths.