Since the 90s, the Executive branch and US Congress has used the Military to do a lot of non-military stuff, that arguably the State Department or other non-military organizations should be doing.
There are a lot of reasons for this:
1. At 600,000+ FTE's, the DoD has the largest number of personnel in the Federal Government
2. Military members are trained not just for their specialty, but to do a wide variety of administrative, management, financial and medical tasks that can be used in non-military capacities.
3. It's often easier to tack on money for non-military specific functions to augment military organizations, than it is to create new organizations.
As a result of this, the DoD is constantly asked to do things that are not directly related to combat in support of international relations, international logistics, basic services and basic research worldwide.