Why were these civilians tried in a military court?

This article on a case from Vietnam could be clearer, but it seems that because one of the defendants was a uniformed official (People's Navy commander Admiral Nguyễn Văn Hiến, shown below with U.S. Secretary of the Navy Ray Mabus), anyone else who was involved in the fraud is also subject to trial by the military courts.

Trial of civilians by military courts contravenes contemporary human rights jurisprudence.