I feel like the logic here is that if companies behave badly enough competitors will emerge and kill the bad company. This school of thought was first pioneered by Robert Bork in the 70s along with the “consumer welfare standard” that hey if you can’t prove it’s hurting consumers then who cares. This is the dominant view of establishment antitrust lawyers to this day and why American industries from chocolate to diapers to national defense are concentrated.

The reality is that if the owners do what they want they will buy competitors, rent seek and not innovate. If the government seeks to meddle they will buy lobbyists. Additionally firms that have their market cornered will squeeze workers and their vendors. Finally close ties between concentrated industry and the government leads to more authoritarian rule.