With a small country, stable government, and national level funding, that's perfectly feasible. I wish that would work in the US, but we have hundreds of transit agencies that do capital projects.

Has nothing to do with size, see Japan and China.

What does it have to do with then?

My understanding japan has a surprisingly private train system, and China fits the model of "works when it's constantly expanding"

Japan is mostly using exactly the model I suggested.

Each of those hundreds of transit agencies are small, but many of them cover populations similar to Switzerland. Some of them cover much larger populations. They should be able to do what so soon as doing entirely within their little agency and yet they are not.