Well an important part of capitalism is preventing monopoly power from being wielded in such a way that it hurts markets.
A market can have significant problems, that hurt consumers, if significant market power is allowed to be used to create anti-competitive consequences.
Capitalism reasonably a system of governance. Politics is all about the distribution of power, and capitalism says that certain parts of society are governed by wealth. Eg. A land owner gets to do stuff on land that they own, or the board gets to choose a ceo.
To make a clearer comparison, we could hold general elections to choose the ceo of Coca-Cola like we do for things that we call "government"
I worded that a bit confusingly, but I assure you I know capitalism is not a system of government. I was using governance as another area where we have ideologies which simply can't be implemented wholesale without some tinkering around the edges.
A market can have significant problems, that hurt consumers, if significant market power is allowed to be used to create anti-competitive consequences.