Central Asia might best be described as “on the road to somewhere.” The most important of ancient empires crossed through Central Asia. Greeks, Romans, Persian, Mongols, and Chinese, plus other smaller cultures passed through this region, on their way to somewhere else.
Perhaps therein lies our answer; people pass through. Central Asia is loaded with mountains, the Hindu Kush, the Pamirs, the Tien Shan. Central Asia is fairly arid, dry, with numerous large deserts and steppes, like the Kara Kum, Kyzyl Kum, and the grasslands in northern Kazakhstan. Arable land is pinched into the narrow margins in the mountain valleys, concentrating people and farmland. Making a living is a challenge in these environments. Imagine Texas, or Oklahoma; now add mountains like those in Colorado.
This is what Central Asia is like. While the region is sparsely inhabited in places, about 80 million people call this region home. The populations are diverse ethnically, and loyalties and allegiances fall along ethnic and tribal lines. Family and tribe devotion means more than devotion to the government. People are far more likely to support or follow their tribal leaders than support the central government. Cultural differences, tribalism, plus the complexity of the natural environment contribute to a realm that is challenging to govern.
Just ask the British, or the Russians.