Mainstream macroeconomic theory -- both in its "freshwater" and "saltwater" traditions -- has become mainstream because of a variety of reasons. The OP quotes

Mainstream macroeconomic theory -- both in its "freshwater" and "saltwater" traditions -- has become mainstream because of a variety of reasons. The OP quotes Keynes: "That it reached conclusions quite different from what the ordinary uninstructed person would expect added, I suppose, to its intellectual prestige. That its teaching, translated into practice, was austere and often unpalatable, lent it virtue. That it was adapted to carry a vast and logical superstructure, gave it beauty. That it could explain much social injustice and apparent cruelty as an inevitable incident in the scheme of progress, and the attempt to change such things as likely on the whole to do more harm than good, commended it to authority. That it afforded a measure of justification to the free activities of the individual capitalist, attracted to it the support of the dominant social force behind authority."[a] That rings true: New macroeconomic theories can become mainstream only if they earn the support (for example, by favoring the vested interests) of educational institutions, governmental institutions, and -- last but not least -- the business establishment. [a] https://ebooks.adelaide.edu.au/k/keynes/john_maynard/k44g/complete.html https://ebooks.adelaide.edu.au/k/keynes/john_maynard/k44g/co...