The New Brandeis movement opposes the school of thought in modern antitrust law that antitrust should center on customer welfare (as generally advocated by the Chicago school of economics). Instead, the New Brandeis movement advocates a broader antimonopoly approach that is concerned with the structure of the economy and market conditions necessary to promote vigorous competition.
Capitalists hate capitalism. They don’t want to compete with other firms, they want a monopoly. So it’s like you’re saying to the monopolists, fine, you want to do capitalism? Well then we’re going to jam so much capitalism down your throat you’ll shit free market competition.