Companies trademarking an artist name after a lawsuit or end of contract should be illegal.
If a company doesnt bother to trademark an artist name to protect their artist from plagiarism during their activities, they shouldnt freaking be allowed to trademark it after that artist decide to leave or ends up in a conflict. Cube was an ass for doing to B2ST, SoMu was an ass for doing it to gfriend, BBC is being an ass for doing it to Chuu.
If you really wanted to protect the names, you should have trademark it at the beginning, trademarking it after conflicts is a power trip.