Perhaps because almost all markets are regulated by the state?
I feel like a broken record here, but there is no such thing as a corporation without the the implicit and explicit grant of privilege by states.
How do you mean "regulated"? Safety standards and such laws? Or something more sinister?
If a few companies in a geographical area decides to cooperate to push up prices, how is this the fault of the state?
Anyone could start a company yet no one did. No barriers of entry from the states perspective.
The prices were artificially high. Just the thing you abhor when it's done by the state, or a state enforced monopoly. But when it's done by market leaders it's fine?
I believe that anyone who abuses monopoly, or monopoly like, power should be punished for it. Wouldn't you agree?