It was a condition of the QRL that both the NRL & QRL affiliated club couldn't have the exact same name and also be run as a separate entity.
If the NRL club went with Redcliffe in their name, they'd forfeit their Hostplus Cup & other senior competitions licenses, which of course they didn't want to do.
Now the outcome may have been the same even if the QRL didn't make this a standing point, but this is one of the reasons the club currently isn't Redcliffe (or Moreton Bay).
As for the moniker, why wouldn't you use Dolphins? It's well suited to a Queensland team, hence Gold Coast wanting to use it, it is one of those animals that is appealing/cute enough for kids, but adults won't have an issue wearing and they can still cash in on their QCup history.
IMO it's better than Firehawks, which we all know would have been Tigers if Wests weren't in the competition, or Bombers and Jets.