Judges sometimes claim that they do not pick winners when they decide antitrust cases. Nothing could be further from the truth.
Competitive conduct by its nature harms competitors, and so if antitrust were merely to prohibit harm to competitors, antitrust would then destroy what it is meant to promote.
What antitrust prohibits, therefore, is not harm to competitors but rather harm to competitors that fails to improve products. Only in this way is antitrust able to distinguish between the good firm that harms competitors by making superior products that consumers love and that competitors cannot match and the bad firm that harms competitors by degrading their products without offering consumers anything better than what came before.
That means, however, that antitrust must pick winners: antitrust must decide what is an improvement and what not. And a more popular search engine is a clear winner.
But one should not take its winningness for granted. For once upon a time there was another winner that the courts always picked, blocking antitrust case after antitrust case. Until one day the courts stopped picking it.
That was the economy of scale.
Woodcock, Ramsi, "Google and Shifting Conceptions of What It Means to Improve a Product" (2020). Law Faculty Popular Media. 56.
Ramsi A. Woodcock, Google and Shifting Conceptions of What It Means to Improve a Product, Truth on the Market: Scholarly Commentary on Law, Economics, and More (Dec. 16, 2020), at https://truthonthemarket.com/2020/12/16/google-and-shifting-conceptions-of-what-it-means-to-improve-a-product/.