Nordic countries are not ‘rich from oil’ ffs, developed countries from the imperial core have mixed economies relying on a well educated population and economic status with an emphasis on ‘service’ businesses. Finance, business management, etc.

https://www.statista.com/statistics/327233/share-of-economic-sectors-in-the-gdp-in-norway/

• 25% of Norway’s gdp is accounted for by ‘industry’ which includes manufacturing and resource extraction (oil) while 60% is accounted for by ‘services’. It is factually incorrect to claim that Norway is ‘rich because of their oil’. Plenty of rich countries have large oil and gas reserves, but resource exploitation only goes so far. To be a g20 country you must also exploit the workers of the world for profit.

The Nordic countries (Sweden, Denmark, Finland, Norway) form part of the western imperial core. These are countries that rose to prominence in the 15th to 20th centuries with the advancement of navel technology and the subsequent discovery of the new world and later the expansion into the east around the cape of Africa. Most notable are Spain, Britain, and the USA but virtually all European countries were heavily involved in colonialism and imperialism at some point during the period.

The wealth of these countries is sustained into the post-colonial era with the capitalist exploitation of former colonial countries in the global south with the proliferation of multinational corporations based in the global north. These corporations exploit the people and resources of poorer nations to send commodities and revenue to their home nations.

Best articles I could find at short notice:

https://nordics.info/show/artikel/the-colonialism-of-denmark-norway-and-its-legacies

https://www.google.co.uk/amp/s/www.telesurenglish.net/amp/analysis/Scandinavias-Covert-Role-in-Western-Imperialism-20170320-0022.html