Some background ... Xinjiang is China's northwestern most province (using an incorrect term, for simplicity). This situation is an intersection of two demographic factors. Those sent to camps are Uighurs, who have avoided assimilating into Chinese culture and who are Muslims. It's not simply that these people in Xinjiang are Muslims, as there is a large, centuries old, very active, mosque in Xining, the capital of neighboring Qinghai Province. Muslims in Xining are of different people groups who have assimilated into Chinese culture (without ceasing to be Muslims).
My daughter is attending a university in Xining and is fluent in Mandarin. She is my source regarding how things are in Xining.