Currently Pakistan has a virtual stranglehold on the goods entering and leaving Afghanistan, and has not hesitated to use it. Pakistan and its Taliban allies are quite upset about the highway, and the murder of Maniyappan is an attempt to stop the construction.
An Indian civil services officer, a remarkable lady who spent seven months in Afghanistan helping the United Nations organize elections writes
I would not like to get into Afghanistan’s politics, but if the Taliban allow roads to be constructed, they would really be losing control. From their point of view, it would just be logical that they make it as uncomfortable as possible for outsiders to reach areas under their control. As long as donkeys take election material and no international observer can reach remote locations, there is no threat to their domain. I had wanted very much to visit some far-flung parts of my province, but security and lack of roads ruled out any such possibility.
Roads are key to where Afghanistan wants to go, to get to schools and health care centres, to banks and factories, and to provide security to the people who have become accustomed to being afraid and helpless. As long as there are no roads, inaccessibility will keep all the dangerous elements safe. The people of the country showed courage and came out to vote on September 18. They trudged along hilly paths avoiding minefields and thorny bushes and rocks in the direction of progress and self-expression. But they need the roads.
I know Maniyappan would have been proud of the work being done by the BRO to give the people of Afghanistan the road they deserve.
From the US Administration's point of view the situation is uncomfortable. On the one hand, this is a road that its ally, the Karzai government, considers to be vital; on the other hand, this is a project that will benefit Iran; and also the US has repeatedly told India to "respect Pakistani sensibilities on Afghanistan". With battle fatigue setting in in the US, it is a race against time to build Afghanistan enough to resist the inevitable abandonment of that country to the mercies of Pakistan and its surrogates.
Update: This UN (.pdf) map on which you can locate Delaram and Zaranj, gives an idea of how this will help reduce the isolation of Southern Afghanistan, which is the Taliban stronghold.