Since when did the NSA become the copyright industry's police? There were no security implications of Kim's operation; why was he targeted by the NSA?
I'm more interested in how much corporate espionage and counter-espionage they do. If a foreign company steals/hacks domestic IP and that hurts the US economy, I wouldn't be surprised if they took action. So, if we can agree that this type of action is reasonable by the NSA, then I could see them justifying the surveillance of Kim Dotcom under industrial counter-surveillance.
See:
Spying on Petrobas, a a Brazilian oil company: https://www.theguardian.com/world/2013/sep/09/nsa-spying-bra...
Spying on an EU Anti-trust official: https://www.cnet.com/news/nsa-spied-on-eu-antitrust-official...
And there are a number of cases where the NSA spied on payment processing companies. I haven't included those because you could argue that those may be related to tracking terrorism funding.