Could be all of the things mentioned so far. Could be the fact there have been fewer Scandies playing internationally recently because of exchange rate issues.
Could also just be an example of the
Texas sharpshooter fallacy.
There are a load of poker tournaments played. Some people win them. A group of these people happen to be similar/come from a similar place. Not necessarily a trend.
I think the US and British players now play against the Scandies with an optimum line in many respects which is another reason along with the tax one. But yeah, as I say in the post, there's no golden age, just a conveyor belt of very talented players coming from online, country unimportant, who are all maybe within a percentage point or two of each other in terms of talent.