Simple, Go to Xinjiang now and see that it's super developed, many cities in Xinjiang look world top class which can put all European cities in shame in terms of infrastructure and urban development, those were all achieved thanks for Xinjiang's peaceful , safe and stable environment.
If China allowed social disturbance and violence, like the terrorist attacks happening in Xinjiang on monthly basis barely a decade ago, those achievements can never be accomplished, people's standard of living can never be greatly boosted to the level that the locals are enjoying now. Almost every family in Xinjiang can afford a car now, it's nothing compare to most places, but compare it to Xinjiang itself in the past, even a decade ago, it's almost unimaginable if you know how poor they were in the not very distant past.
