"Chinese" mummies is a bit misleading. The Tarim Basin has a long history of Chinese rule/influence, but not that far back.
These mummies are from a unique population that descended largely from Ancient North Eurasians, a group who contributed smaller percentages of ancestry to Northern Chinese people, Europeans, Siberians and Native Americans.
So these cheese enthusiasts are less Chinese and more like distant foreign relatives to the Chinese who adopted dairy-heavy pastoralism after it expanded through the steppe.