I read something a very long time ago now, by someone on the ground as the final troops left, I think. Military anyway. Their take was that by the end of the war there were a LOT of broken soldiers, the ones from deep Red states, with family history of honourable military service fighting for freedom. They found themselves not knowing what they were fighting for or why they weren’t winning. In the end they couldn’t face returning and facing adoration for their actions. And they couldn’t face the scorn of their community if they turned peacenik and they couldn’t face a lifetime of pretending it was about honour and freedom. Apparently some number of them just walked away near the end. The COs couldn’t bring themselves to record them, soldiers who’d given sooo much, as deserters. It was just better to call it MIA. Sightings of them, from time to time, in part gave rise to the theories the Vietnamese are holding POA’s he said, etc.
It was so long ago, over 30yrs, that I read this interview. And I admittedly cannot provide a site. But I remember it because it had the ring of truth to it, for me, and was something I had never even considered.