The majority of Vietnamese population at that time made a living out of farming. Rice fields, fishing, basic agriculture. Pretty much all the boys that signed up the join the NVA from ages 14-25 knew nothing but their villages and fields. So the US might not have lost to a bunch of farmers armed with pitchforks, they did indeed lose to a bunch (by a bunch I mean a few million) of farmers armed with Soviet arms and tanks and rockets and airplanes. After the war the majority of them also returned to farming, while the rest went to other manufacturing jobs and businesses.