It's just so obvious. I don't get how people don't understand: a strong, publicly funded, centralized authority is the most effective way to fund and scale infrastructure.
Privitization is wasteful and fragmented. Infrastructure should not be a for-profit enterprise. The state is the only logical solution for public works like this.
The US experienced this with the highway system - which is the US equivalent of the Chinese high speed rail network in terms of scale for the US at the time. Over 78,000 kilometers in 35 years, with major routes completed much earlier. Massive government spending (taxes & bonds) directed toward a publicly beneficial infrastructure project completed in record time. It has been highly successful despite efforts to privatize the construction of for-profit toll roads and privitizing the maintenance of the highway system, causing serious degradation of many of the roads and bridges.