More from the article...

...HLN, once known as Headline News, will simulcast CNN's morning show in place of its current morning news program. The network had already been airing true-crime shows through much of the day. While the live programming will go away, the staff will join forces with the company's ID network and develop or acquire true crime programming for both channels, the person said....

That's probably why HLN had a marathon showing of Sorkin's excellent West Wing show a few days ago...

Take up space during the transition....

@#2 ... I never understood the logic behind completely rebranding stations like this ...

The logic is business.

CNN has this other channel on cable TV systems. So, how can they exploit that other channel for profit?

The call-letters do not matter (think TNN[1] which morphed into Spike, then Paramount, then...?).

What matters is ... how many viewers can be attracted so that the cable companies will continue to carry the formerly dead channel.