Mike Forces weren't ARVN. They were specifically recruited and trained by (Army) Special Forces advisors in Vietnam from the early 1960's on from ethnic minority populations that didn't like the ethnic Vietnamese, so they were eager to fight the PAVN/VC forces as a matter of survival.

After the war, these minorities were punished very harshly -- a lot of them were evacuated to the states or escaped on boats to come here. They were definitely some of the most loyal allies the US had and we sort of left them to their fate when we pulled out.