The problem is content producers on Youtube are actually losing money because their title has the word "REACT" in it and the contentID that automates detection of infringing videos are tagging these videos so the creators are losing their ad revenue and getting strikes against their account.
Another problem is that these guys have millions of subscribers so their a big revenue stream for Youtube so they have of course sided with the Fine Brothers.
The Fine Brothers didn't create this kind of content. They are nowhere near the first to use it but they are still basically taking ownership of other people's ideas.
I've subscribed to uploaders who've had these problems and Youtube is notoriously difficult to deal with because you have to prove you're not stealing, instead of the accuser having to make a proper case.
Just today I saw a video of a quad-copter being attacked by a hawk, and it was uploaded by the original owner but the video was flagged by some Korean news agency as theirs even though they had no relation to the video aside from using it in their broadcast. The big stinker is that the uploader was donating the ad revenue to a charity and so they've lost out on a couple grand already.
The system Youtube is using is very flawed but they don't seem to care about the grief and frustration they are causing users.
The most satisfying thing is a live stream of the Fine Bros current number of subscribers and the number just kept plummeting by 20-30 every few seconds.