A bunch of journalists actually went to China to see the abuse for themselves and didn't walk away with anything to support that narrative. Best they could say to defend their case was "China is hiding the truth, that's why we didn't see anything" Over time, all the claims the right made about the "genocide" were slowly being deconfirmed to the point that it was becoming clear it was all made up. Is there a chance that some of the stuff actually was right? Maybe, but when you know it came from a place of bad faith you don't exactly need to waste energy debunking each and every claim from the likes of faith healers and flat earthers when they have a rich history of flat out lying to drive a narrative.

When people actively invested in finding out fucked up shit can't find any fucked up shit, it's a pretty good sign it's not happening.

EDIT: Doesn't help that a lot of the people making the biggest fuss about the Uighurs are all siding with Israel in their genocide. One of the big key things that genocide deniers do is make a big stink about fake genocides that they made up on the spot (Fx: the great replacement)