I urge those who are interested to read (as you did) the Wikipedia article about it.
In addition to the their explanation, I must add that the Law of Jante (Janteloven in Norwegian) is much more present in Norway than in the other Scandinavian countries: https://en.wikipedia.org/w/index.php?search=Law+of+Jante&title=Special:Search
I will now try to explain how the Law of Jante has affected Haakon and Mette-Marit's popularity:
As I said in post 109: After the criticism from people/media calmed down after the wedding in 2001, both Haakon and Mette-Marit become very popular (I would say even more popular than what Frederik and Mary are in Denmark now). They got some criticism for the controversial journey they went on in 2010/2011, but it calmed down quickly. Their approval ratings were above 80% until early 2013.
This was because we liked that they were like us, we liked that Mette-Marit had a history and we liked that Haakon was a caring stepfather to Marius.
In the last 3 years, this has unfortunately changed. Let me make some examples:
They have been criticized for:
1. They took the children out of the public school etc.
Most Norwegians reacted like this: They think they're better than everyone else. They don't think that the public school is good enough for them. Who the heck do they think they are.
2. Being friends with wealthy people, politicians, actors and for going on luxury boat-trips etc.
Most Norwegians reacted like this: They are snobbish. They are not like the King. They live like royalty did in the past. They are trying to reintroduce the nobility in Norway etc.
3. Haakon: He interferes in politics, uses the royal court's money to build organizations and is bad at dealing with the media.
Most Norwegians reacted like this: He behaves like a politician. He is arrogant etc.
4. Mette-Marit: She's even worse at dealing with the media and gets cranky when she gets asked critical questions. And she uses expensive clothing.
Most Norwegians reacted like this: She is arrogant. She can't handle criticism. She is snobbish. She is too grand etc.
Queen Sonja was also criticized for being snobbish, a bit cold and too grand, but it has calmed down over the past 10 years.