If anyone is wondering why the POW/MIA flag is a thing in U.S. politics, you should really read up on it because its a fascinating example of boomer brainworms.
After the Vietnamese got good at shooting down U.S. aircraft, the U.S. tried to massage casualty figures by reporting the dead aircrews as missing. Except their families took the Pentagon at its word and believed they were truly prisoners, and began agitating to get a political deal to bring them home. As the war dragged on into the 70s the Pentagon started using the families as propaganda for a lost war, acting like they needed to prolong the war to save the thousands of imprisoned airmen. Subsequently, grifters started selling all kinds of POW merchandise to draw attention to the thousands of U.S. soldiers that Nixon claimed were still imprisoned in Vietnam.
Then the war ended, and the five hundred or so guys that really were prisoners came home, and you'd think the gravy train would end there as the truth came out, but no, Americans believed it was all a hoax. The government was covering something up, and there must really be more than a thousand US soldiers still held in Vietnam.
More POW merchandise was sold than ever before, there were blockbuster movies about going back to Vietnam to free the prisoners, there were flyovers for the POWs at football stadiums. Ronald Reagan himself believed it and made threats to resume bombing if the soldiers weren't returned. Americans started traveling to Vietnam to buy information about the POWs and try to bribe people to secure their release, and a lot of Vietnamese people got free money selling bogus rumors and scraps of old US uniforms. This shit continued well into the 90s, with every president giving a big speech for the POW families every year, and the US being unable to normalize relations with Vietnam until almost the 2000s because of it.