I think there’s a variety of complex legal, political, and technical reasons why torrent sites can avoid having their domain “seized”, but I think the summary is: there be dragons here and it’s not worth playing around with.

Politically, some jurisdictions define piracy differently and hosts won’t comply with legal threats from the US.

Legally, hosting a torrent is not the same as hosting a ROM. In the former case the actual copyright works are hosted by users, the torrent site just hosts the torrent file which is a list of users from whom you can download the content. ROM sites tend to provide the actual file for download, which contravenes relevant copyright laws.

Technically, you don’t need a commercial host platform to operate a website. It’s entirely possible to host a site in your mum’s basement on your laptop. Obviously for a large site you’ll want more appropriate hardware but the point is larger torrent sites are likely to run on hardware maintained directly by the admins.

The most compelling reason not to get involved in a public facing grey area site like ROM or abandonware hosting, is that it doesn’t really matter where you stand with the law - you won’t have the resources to defend yourself. Suppose Nintendo decides they don’t like you doing what you’re doing. They have an army of sophisticated lawyers who have spent a lifetime learning how to weaponise the law. It doesn’t really matter who’s “right”, all that matters is how much money you have with which to engage lawyers to defend yourself.