I don't know about Norway's taxes, but I assume trading was his first source of income, so just like everywhere else in Europe( UK, France, Germany, Spain, Switzerland...), he must be paying income tax( + social security...) on his trading gains instead of capital gains tax. Either that or he was incorporated. Perhaps I am wrong but I doubt he was only paying 25 % in a scandinavian country...
Norway has wealth tax, probably a bunch of mandatory social security/solidarity taxes and I suspect Aas' trading income would be taxed as income rather than cap gains, which is the case in most western european countries (Sweden and Nederlands beeing exceptions, there might be others). Not going to google the issue now, but Norway and France usually battle for the top spot on the list of highest taxed countries in the world. One could reread articles about Aas and probably find out how much he actually paid, although this might leave aside wealth and other social security taxes. Income and cap gain are only part of the total tax bill in highly taxed Europe, some extra taxes are non negligeable.
Norway has a large sovereign wealth fund, mostly funded by taxes, how do you infer from that it has taxes pretty similar to US ? Besides I wouldn't call the US a low tax country, although differences seem to be important from state to state.
Yes, taxes on the oil industry, not sure why Beerfan brought it up when pushing the point Norway and US taxes are similar. But the future looks bright for Norwegians, that's a huge fund for a small country. A bit more worrying is the country having the reputation of being the most controlled by its government in Europe (Something like "the last Soviet state in Europe"), but people don't seem to care that much there. Travelled a few times to norway and liked it very much btw. "The purpose of the fund is to invest parts of the large surplus generated by the Norwegian petroleum sector, mainly from taxes of companies but also payment for licenses to explore for oil as well as the State's Direct Financial Interest and dividends from the partly state-owned Equinor." https://en.wikipedia.org/wiki/Government_Pension_Fund_of_Norway
Norwegian oil fields are nationalized. The major source of revenue is not from taxes but from direct profits in oil production. Equinor (former Statoil) is majority owned by the Norwegian state and has a revenue of $62B. https://en.m.wikipedia.org/wiki/Equinor