This week's TIME cover story points out the multiple ironies of NBC's decision to put Jay Leno in primetime. It's also a good snapshot of the TV business as it is today:

But the difference between Conan's and Jay's Tonight is not just about personal style; it's about two different philosophies of TV.

The idea behind giving Conan Tonight is that there are no more Johnny Carsons. No one is going to unite a mass audience of all ages and persuasions and from all walks of life every night.
...
And yet few entertainers are more antithetical to this idea of niche programming than Leno, Mr. Big Tent...

Leno grew up when mass media were mass. He recalls how "comforting" it was to watch Eric Sevareid with his parents, before kids had TVs in their rooms and a different network for every stage of childhood.

After reading the article, I don't find the decision too surprising, more like, why didn't they do this years ago? And I'm really glad Jay Leno is going to be back on TV. Somehow Conan just doesn't do it for me.