Since it was asked before why would Nintendo complain about ROM hacks on youtube yet do nothing to repro makers?
The answer is: probably because it's easier for Nintendo to do. All they need to do is file a complaint to youtube.
There was a time Nightcrawler tried to take down a repro maker making repros of his translation patches. I believe he reported the repro maker to his ISP or US-based website host or whatever. Something like that.
Site went down for like a day or something maybe until the repro maker just found a new host in like the Middle East or Asia, somewhere known to be more tolerant of copyright infringement.
Even though if they're in the US, Nintendo could probably sue the site owner directly, but I'm assuming there's quite of bureaucratic legal work they'd still have to work through to make it all formal and such.
In my opinion this is also a big fault of youtube. Content ID matching allows a lot of false positives, and also false negatives (flip or slow down footage). There's barely any human reviewing going on unless you're part of a multi-channel network that has a legal team (polaris, machinima, etc.). Bigger channels can usually make a successful counterclaim, but the smaller fry will almost always get hit by an unfair strike. Nintendo profits from this by simply feeding nearly all their game footage into content ID. Nintendo footage from a channel not associated from them? Bam, instant ad profits to Nintendo withheld, until a counterclaim. Even if you're doing a review or showing sample footage you still can be hit by a penalty or even lose your youtube account. YT is so big nowadays that you can't get around them, so if you want your video to get noticed there aren't that many sites to go to.
Then there's also manual takedowns. If you as a company don't like that one review made by a youtuber, simply file a complaint and YT will remove it instantly. Usually it takes several days before that video shows up after a successful counterclaim. Incidents like those are too many to count, and unless your channel is big enough to make a fuss out of it, you won't see that video ever again. For big channels this is usually positive for them, because the fuss gives them more publicity if they speak out against it, but smaller channels won't be heard.