It's probably not a stretch to say Nelson has a strong dislike for the Canes. This is going back to 2019, but when the Canes swept the Isles in the 2nd round I think it was, there was that weirdness where he patted Curtis McElhinney on the helmet after the Isles scored a goal for some bizarre reason. Canes obviously did not appreciate this bizarre behavior and in the handshake line, Dougie Hamilton returned the favour by patting Brock on the head.
Combine this with losing to Carolina last year, then being down 2-0 this year, having him randomly erupt after the ENG yesterday to cap off that meltdown isn't unexplainable.