President Xi Jinping, the party chief, laid the groundwork for the crackdown in a series of speeches delivered in private to officials during and after a visit to Xinjiang in April 2014, just weeks after Uighur militants stabbed more than 150 people at a train station, killing 31. Mr. Xi called for an all-out “struggle against terrorism, infiltration and separatism” using the “organs of dictatorship,” and showing “absolutely no mercy.” ...
... The internment camps in Xinjiang expanded rapidly after the appointment in August 2016 of Chen Quanguo, a zealous new party boss for the region. He distributed Mr. Xi’s speeches to justify the campaign and exhorted officials to “round up everyone who should be rounded up.”
The crackdown encountered doubts and resistance from local officials who feared it would exacerbate ethnic tensions and stifle economic growth. Mr. Chen responded by purging officials suspected of standing in his way, including one county leader who was jailed after quietly releasing thousands of inmates from the camps.
https://www.nytimes.com/interactive/2019/11/16/world/asia/ch...
The most striking sentence in the NYT report is this one, describing the alleged motivations for the leak:
Though it is unclear how the documents were gathered and selected, the leak suggests greater discontent inside the party apparatus over the crackdown than previously known. The papers were brought to light by a member of the Chinese political establishment who requested anonymity and expressed hope that their disclosure would prevent party leaders, including Mr. Xi, from escaping culpability for the mass detentions.