Policy change was in response to violent 2008 Tibetan and 2009 Ürümqi / Uyghur riots (~200 deaths). The blame was placed on then relatively unfiltered western social networking sites which solidified ethic identity that was nominally accepted under old MingZu policy. In the case of Uyghurs, easy dissemination of foreign Islamic texts led to pockets of radicalization (Turkistan Islamic Party) turned violent extremism. Incidentally post riot was when Facebook and twitter was blocked. Western narrative was information control, but additional domestic rationale was to prevent escalation of violence since the riots targeted Han Chinese, and Han nationalists (who hated minority affirmative action privileges - we truthfully are cut from same cloth) were calling for violent retaliation. Basically, the CPC wanted to filter the internet to prevent race wars.

Twitter and Facebook took the moral high road only to be confronted with the same problems now and converging onto the same solutions. Anyway these incidents led Chinese thinkers to reexamine the ethnic policy based around oblast multiculturalism + carrots which was suppose to produce stability but ended up challenging serenity. Now the policy is forced integration via work camps. Somewhat tried and true. Chen QuanGuo was appointed Party Secretary of Tibet, he began security policies that enabled Tibet to see some of the highest GDP growth in the country. He was moved to Xinjiang a 5 years later to replicate his work, expanded the security architecture into the camps (however people want to label it) and increased anti-terrorism efforts. There's been no attacks since his reign, many before. Got promoted to political bureau member for his work.

MingZu policy change is not well known, mostly information disseminated between China scholars. TBH most western reporting on China is naive because western news room simply don't have sufficient assets covering China which is already a very difficult reporting environment. It doesn't help that foreign desks are full of white dudes who can't speak the language. Regardless, since the subject is justifiably mass human rights abuse, I think people don't really care about nuance even why something is happening, just that it is. Which is fair, you can't expect much on Chinese reporting when folks exposure to Chinese affairs outside of MSM are two youtubers playing the clickbait game. It's a ridiculous state of affairs.

I don't know about future timeline, Xinjiang is 7x larger than Tibet which took 5 years and is still ongoing. CPC probably hoping to do a reeducation "lite" policy in HK via CPC textbooks. They blame the current protests on a generation raised by British civics textbooks. I think the summation is, we focused too much on 2 systems instead of 1 country. Salad Bowl instead of melting pot.