There’s a huge difference between why there’s sufficient evidence to the occurrance of the Holocauast, and why the average liberal believes it. The latter has nothing to do with the reasons you’ve given, they believe because they’ve been told enough times to accept it. As far as they know, there’s as much evidence for the hololdomor and literally anthing bad that could be happening in Xinjiang. There have been a comparable number of headlines saying “there be genocide here” for the others, and that’s the level of scrutiny they have.