Why is Afghanistan unstable?

In his recent Newyorker article Barnett Rubin discusses Why Afghanistan still unstable? and argues that stabilising it was not the goal of U.S. policy: http://www.newyorker.com/news/news-desk/what-have-we-been-doing-in-afghanistan?intcid=mod-latest

I have thought of a good method of approaching this, imagine a couple of scenarios: 

Scenario A. 

1. create professional army, starting off with the remnants of DPA armed forces.
2. Economic development 

3. Integrate Afghanistan into international political and economic system. 

4. Foster national leadership. 

5. collect weapons.

Scenario B

1. Arm and fund militia with history of human rights abuse and atrocities to fight dissent by labelling it the Taliban. it was only this year that the US recognised Taliban as a political group and conceded to a political instead of military solution. 

2. AID, AID and AID which only delivers assistance to very few and leaves out the majority to fend for themselves. Treating the symptom of poverty while ignoring the fragile state which is the real cause.

3. No significant trade treaty and no long term strategic partnership; relationship at its low of all time with neighbours. 

4. Warlords, drug lords and criminals were promoted by giving them a share in ruling the country. 

you guessed it right, it was the second that unfolded. 

sure the lack of Afghan leadership had its devastating impact and of course the dysfunctions of Afghan culture rendered it unable to take advantage of international presence and certainly the lack of Afghan human capital and skills was not conducive to the occasional efforts of US at state building. but if you are studying the role of the US as the most significant player in Afghanistan then you need to look at its policies, conduct and practices. This is escaping people today and it is significant because we need to recognise the responsibility of the US in what is happening in Afghanistan today. we also need to understand the underpinning reasons for the choices organisations and politicians make and the assumptions they had made.