[Nyan]

A possibility might be that the bigger sites have paid more attention to opsec, and are harder to take down, whilst smaller players may be easier to intimidate.

Current Nyaa (nyaa.si) has been targeted [https://torrentfreak.com/mpa-lawyers-are-trying-to-shut-down...], but efforts haven't been successful so far.

> I guess because these are commercial?

Highly unlikely - it's not like rights holders get anything regardless of commercial status. Also, Nyaa runs ads on their NSFW site, so it's commercial in that respect.