The factor that significantly contributed to the lack of stability and freedom in Afghanistan is the Taliban take-over of the country.
The Taliban's rule, which began in the mid-1990s and was re-established in 2021, led to strict enforcement of their interpretation of Islamic law, significant human rights abuses, repression of women, and ongoing conflict with various groups within Afghanistan, which destabilized the country further.
While the other factors mentioned (Britain's historical involvement in the region, religious conflicts, and India-Pakistan tensions) have played roles in the broader historical context of instability in South Asia, the immediate and direct impact of the Taliban's governance has had a profound effect on Afghanistan's stability and freedom in recent decades.