It's the combination of being a Nordic social democratic + having large oil reserves.
And more importantly: not spending the money from that oil wealth in a stupid way but setting it up to generate future revenue streams that benefit everybody. As opposed to other countries which squandered their riches on short term stuff.
To be fair, there is not really any other country to compare them to on this. No country which was already rich, stable, democratic and well-educated has ever received such a large resources windfall as Norway did from North Sea Oil.
NL, UK.
NL has a far, far smaller share of North Sea Oil than Norway (and 3 times the population)
The UK has a similar share (actually slightly smaller) with over 10 times the population.
All the more reason to use that windfall responsibly and to preserve the proceeds. NL in particular was extremely wasteful, especially with their natural gas resources which were sold for a ridiculously low amount to foreign customers, and which they now re-import at much inflated prices.
You seem to be making a political point about the Netherlands which is completely separate from the fact which I presented, and which you incorrectly contradicted.
Haha. Good luck with that attitude here.
Sweden is doing pretty well too. No oil there.
Sweden is a pretty impressive industrial exporter.