What I've found to be fascinating is how polarized Jimmy Fallon's taking over the Tonight Show has been on different websites with comments like Yahoo or Entertainment Weekly or People. Some of the people think he's too liberal and that NBC was "too threatened" by Jay Leno's conservatism. Other comments have said that Jimmy Fallon is just a suckup who sucked up to NBC to take Jay Leno's job away. It's made the whole thing almost a political or generational thing. It may be a generational thing, as Jimmy Fallon understands social media in a way that Conan sort of did and Craig Fergusson sort of does.
I'm not a Leno fan, but I do think the network has been tired of him for some time despite the fact that he brings in the ratings. The impression I got was that TPTB wanted to keep the Leno rating but also bring in a younger demographer. I think that was part of the logic in the Conan take over. I also think like in the case of Anne Curry, it was Conan's "time". In other word s the network could no longer justify not giving him a chance. However just as in the case of Anne, they kept backup on hand. In Conan's case they simply gave Jay a 10pm slot.
With Jimmy the network had a safer bet because Jimmy is fairly non threatening. I do think Jimmy benefited from being by Lorne and the network, but I don;t think it was with the intent to go after Jay's job. As for round 2 of the "late night wars". I do think there is a grain of truth to it. I don;t think they are preventing folks from going on the others shows, but I could see a more aggressive push being put out there to come talk to Jimmy first.