Earlier quoted context omitted.
So what you want is a command economy? Nah, I’ll pass. Markets are made up of people, they’re not just some abstraction. Governments have good uses, but determining who is participating in what market and how much market share they have or are allowed to have isn’t one of them.
How do governments prevent monopolies? That's been generally done and supported for over a century.
Proving a monopoly exists or are forming could be another way to do so, but so far they have recently made lackluster arguments in Courts of Law on that front.
If you then prove a monopoly, can you also then prove that it’s activities are harmful to the people in the marketplace by denying them choices they would otherwise have? Maybe, but probably not very often and certainly not easily.