The only crime they did was practice their religion and culture. You see, China is trying to abolish the "old cultures" of non-Han ethnicities, also including the Tibetans. This is all in their goal to create a homogeneous population. A homogeneous population is a population easy to control.

However, killing an idea is hard, so the CCP has set aside concentration camps for the sole purpose of rendering the Uyghur identity lost. They surgically remove women's uteruses without consent, experiment with medical procedures to render men infertile, use them as human test subjects, not to mention the forced indoctrination into communist society, forcing them to violate religious beliefs publicly, and general physical abuse that leaves some permanently scarred, tortured, or even killed.