During the Vietnam War, why were the Monta Gnad Mountain people on the border between South Vietnam and Cambodia willing to be the running dogs of the US special forces to help the US military deal wi

During the Vietnam War, why were the Monta Gnad Mountain people on the border between South Vietnam and Cambodia willing to be the running dogs of the US special forces to help the US military deal with the Viet Cong? At that time, not only the people of Gnad, Monta, but also several mountain tribes, such as Miao, supported the US military, mainly to resist the invasion of the Jing nationality.

Gnad people in Monta belong to a mixture of Khmer language family and Austronesian language family. They are subjects of the former city occupying power and Cambodia. The area where they lived was not occupied by Vietnam until 18 ~ 19 century. The Vietnamese adopted a series of policies of destruction, immigration and assimilation in this area, which aroused the resistance of the local people.