Just cutting this, not trying to diminish what Volpone said, just wanted to help clarify certain points.
The Tonight Show started with
Steve Allen in 1954, a companion in essence to The Today Show. Then Paar, Carson, Leno, O'Brien, Leno, and now
Jimmy Fallon.
Late Night hasn't had as much controversy in hosting, and has gone from Letterman on to O'Brien, Jimmy Fallon, and it's current host
Seth Meyers.
The Late Late Show has been a bit murky. It was popularized by
Tom Snyder, and it was merely a one-on-one interview show with no audience. That was changed when
Craig Kilborn from Daily Show and ESPN fame took over the show and it became a more mainstream talk show. Kilborn left and was replaced by
Craig Ferguson, a Scottish comedian known at the time for playing Mr. Wick on The Drew Carey show. After LLS he's bounced around various shows including an emmy-winning stint on daytime game show Celebrity Name Game. It was believed he would replace Letterman when he left The Late Show, but when it became apparent he wasn't getting the gig, he gave even less of a fuck hosting the show until his exit. He was replaced by
James Corden, a British comedian known for Gavin & Stacey and Doctor Who. He turned it into more of a Graham Norton type show, but it still pulled in fans. After he left, the show was kaput, and they went with the @ftermidnight show hosted by
Taylor Tomlinson, but she wanted to go back to stand-up, so the entire time slot was vacated.
As for
Conan O'Brien after the Tonight Show debacle, he would eventually start a show on cable station TBS (Turner Broadcasting System) simply called
CONAN. Andy Richter returned as his sidekick, and most of his band would carry over, now known as
The Basic Cable Band, led by Jimmy Vivino. He would stay with TBS from 2010 to 2021, although the last three years went from 60 minutes to 30 minutes.
Truth be told, Late Night talk shows are a dying breed. Late Night with Seth Meyers is the only one post-12:30 left, and as Volpone pointed out, mostly due to it being a Franchise like The Tonight Show. The fact that SNL's Lorne Michaels is the producer of both Tonight and Late Night may have something to do with it also, but with his eventual retirement on SNL, the writing may be on the wall for his eventual departure from the Late Night shows as well. But as for The Late Show with Stephen Colbert... yeah this is all bullshit.