Notch has previously appeared on Swedish television of course, since he's basically a national hero these days in Sweden. This is his first appearance on network television with a nation-wide audience in the United States.
During the interview Craig Ferguson, speaking about Minecraft, says, "Anyone below the age of 20 seems to be obsessed with this thing." And there we have the reason why Notch was asked to appear on the show.
Television shows are constantly competing for viewers in order to do well in the ratings and thus charge more for ads. The TV industry is so old-fashioned that the ratings aren't gathered continuously—they're only tallied during certain sweeps months. November is a sweeps month.
Since Minecraft has sold over 33 million copies across all platforms (12.6 million copies on PC), that's a lot of potential viewers for Craig's show. Since most gamers and people under 20 don't watch live TV, it's a lot of potential new viewers for Craig's show. Even if only for that night, every viewer helps during sweeps month.
Did Minecraft players approve? His appearance was received quite well on Reddit.
As expected, Notch's TV appearance was well-reported in the gaming press—joystiq, GamePolitics, the escapist, Kotaku, PCGamesN, and StrategyInformer all had items.
This TV appearance by Notch is another indication that Minecraft is going mainstream.
The TV site Zap2it had an item: 'Minecraft' creator Notch visits 'Late Late Show with Craig Ferguson' for first talk show appearance. This piece isn't written for gamers, it's aimed at a general audience who might not know who Notch is.
In addition to mentioning his TV appearance, the tech site CNET has an interview with Notch and says Minecraft is "…becoming a cornerstone within video gaming's greater assimilation into pop culture." It also points out the recent South Park episode in which Minecraft is a central theme (full episode viewable here).
As Minecraft becomes a household word it's showing up in more and more places.
This article is an extended version of an earlier post I made to the Minecraft forum.