It doesn't have to be as efficient ... a hyper-efficient private business that shift most of it's profits to a tax haven (as they all do) provides less benefit to the country than a moderately efficient state enterprise that invests all the gains back into the country.

The point is for the country to take the role of "business owner", and to relegate the private businesses to the role of an "employee" (with a commensurately smaller slice of the upside) ... and if they don't like it, someone else will take their place ... after all the country has a guaranteed monopoly (they own the entire resource).