The rest of that first sentence is basically a "hedge", where the writer is admitting that his first statement may not be completely true, but is "close enough to true" that he felt justified in making it.
In the first part of the statement, he basically said "According to the data, this is a Utopian society", which is to say, a perfect place where everything is good and everyone is happy. Human nature being what it is, however, such a place has never existed and probably cannot actually exist. In the second part, therefore, the writer tacitly admits this; it basically says "(okay, it's not really a utopia, but) at least it's as close as we have gotten to [a utopia] so far."
For the second section, yes, the sentence is correct.
If you strip away all the fluff, the core of the sentence is:
Why has this region proved so successful?
The subject is region. Since we are only asking about one region, "has" is the correct verb to use.
There is also a relative clause, which adds information about the region: specifically, it is a region "with freezing winters and expanses of wilderness". Since we already know what region we are talking about and are just giving extra details about it, we set of the relative clause with commas.
(An expanse of wilderness is simply a large area with no human-made modifications; it is "as nature left it", presumably full of wild animals, dangerous geographical features, poisonous bushes, and other hazards that mankind would normally wipe out in the course of rendering the area 'fit for human habitation'. The writer is contrasting the harsh, unwelcoming nature of the region with the presence of this utopian society and wondering how such a perfect society came to exist in such an unlikely-seeming location.)