At end of the day repressing restive frontier minority that accounts for less than 1% of population for domestic security (especially terrorism) is the "correct" political decision for CCP. There isn't any feasible calculus for not taming XJ (or Tibet or HK or TW). The real answer is they were left alone for too long due difficult access (whether by geography or politics), granted privileges in hopes they would not stir up trouble. That didn't work, and now wealthier PRC can build high speed rail into their provinces to forcefully integrate. Something every other Chinese province was subject to post 50s. In short, it's simply their turn.
Even the most pessimistic Zenz estimates of XJ internment at 1/12 of population is roughly lifetime incarceration level of US blacks. And the hit job articles on XJ vocational/reeducational "slave" labour programs still have "inmates" paid dramatically better than US prison labour in absolute terms and substantially better in regional terms. Exceeding ~40% of 600M Han Chinese subsisting on informal wage economy. Han Chinese would lose their shit if they find out the amount of subsidies going into XJ securitization and sinicization. If they the the choice between spending trillions to "tame the savage" in XJ versus 12M bullets for an actual genocide, the amount that would pick the latter would be disturbing.
US tried to nation build and spread western values in Afghanistan - PRC is nation building in XJ and spreading PRC values. Just with less bombs and more infrastructure.