I just read the article and realised that the top users are also from the world economic or political powers such as the US, China and Russia. This is also due to the level of awareness and technological advancement which the citizens have taken advantage of too. You won't expect people from poorer countries to have easy access to such information and technology.
Statistically, Bitcoin users are dominated by users in developed countries, this is because people in developed countries have high access to information and technology. Infrastructure is a benchmark for determining how many users access Bitcoin. Poor countries really don't access Bitcoin too much, this is because infrastructure is still limited because crypto access really requires internet networks and computer devices such as smartphones and various other sophisticated hardware.