The ship could have been sold. Older ships are often sold to smaller operators.
Retrofitting is another. The ship gets enlarged and gets a whole new theme or design. The Carnival Destiny just became the Sunshine after a major overhaul. It's part of the rechristening process. She's no longer the same ship in many people's eyes, so,they give it a new name.
No big deal.
In the case of new ownership, a lot has to do with superstition. A new owner always gives a ship or boat a new name.
CCL has begun the process of changing names of ships that just went under complete refurbishing... they feel that the new extras an ammenities warrant a name change due to it feelining like ' a completely new ship'. This should go into affect sometime next year.
They go into the witness protection program ?
@BAK LOL! This isn't the crappy ship it was before... it's completely new! Look its not even the same name! hahah