It looks to me that he had become a boy toy (Bacha Bazi), an all too common situation in Afghanistan.
In the history of Islam, going back to the time of the Prophet, pre-pubescent boys were not considered men, and were therefor exempt from prohibitions on homosexuality. Young boys for sex have been a significant part of the Islamic slave trade ever since. They grow up, and Afghan society is full of them. The warlord's were famous for flaunting elaborately decorated Bacha Bazi during the Civil War, and they are a common "perk" for powerful men in Afghanistan today, especially in the North.
Here is an example of a characteristic outfit for a dancing boy, which resembles Bergdahl's:
