The cost of acquiring rights to the Condor name may be modest. The cost of rebranding Eurowings to Condor and communicating that message across Europe will be high. The Germanwings brand was replaced by Eurowings partly to allow for neutral brand expansion (and yes, also to cut staff salaries)
There would need to be a very compelling reason for rebranding Eurowings to Condor to outweigh the costs involved