Why did britain and russia become involved in a “great game” in central asia?

 Imperial rivalry over Afghanistan and central Asia catapulted by the quick rise of Russian interests in the region.

The British empire was quickly being threatened by the growing influence of Russia, in the 1830's in central Asia, for they felt this threatened their imperial interests in India. The Russian empire too was wary of British influence in the region, and specifically Afghanistan and other middle Asia countries. It was simply a diplomatic and political confrontation over the two powers imperial interests in the region.

Treated as a slave is cruel and harsh