What's the background on Arlanda Express. I've used it and wasn't too impressed but it wasn't late or super slow. Though I wouldn't consider it an express connection from the airport to central station compared to what's possible on rails.
Basically the government put up much of the financing but gave a private company monopoly on traffic until 2040. It was sold to venture capital which because of tax planning are paying little to no tax.
Liberal economic policy states that profit is the domain of the private enterprise, infrastructure that can't turn a profit is the domain of the state. I think it's a crazy idea, but that's the gist: if there's money to be made the government should leave that to private business and trust the invisible hand to make things right.
Because the government should run the country and not small companies.
If the company is exploiting strategic resources like oil it should be taxed, not owned as far as I am concerned.
More seriously, to finance populistic reforms to increase the power of their own party.