Perhaps an Admiral was brought in because Naval forces were assisting in the recovery of the plane. But, at the time, there were rumors that the Iranian Government was behind the downing of the plane, and the Iranians were rejoicing. I still wonder if what had happened was a "shoe bomb."
Military resources are used many times assisting after disasters, both natural and man-made. I cannot think of any aviation disaster where the NTSB was not the lead investigator and in full control of all press briefings!