It is not exactly that Norway bought bitcoin and put it on pension funds. They have an oil fund which comes from all the Oil income they have, unlike some other countries they do not spend it on silly stuff because politicians there are actually smart people and decent people (well could be bad compared to their countrymen if you dislike them as a Norwegian but certainly better than American ones or some other nations politicians).
So, instead of spending that money on useless stuff, they are managing it to make it bigger, and the managers of that fund also own money on mictostrategy which means that indirectly Norwegian Oil does own some bitcoins from that investment.