Norway is a small country with proud people and songs performed by native artists always get a special attention. The same with Sweden. 14 songs from the national selection are sitting in the Top 40 now, where 4 of them have topped it. What do we have now? Right - Las Vegas is #1.
Then the positions in the chart are changing every week depending on the singles' sale. Even if there are always better songs, they need time to climb the charts and they can't stay there for ever.