One thing that puzzled me when I was reading about the Vietnamese war was the fact that during the invasion of South Vietnam, North Vietnamese army had far less mechanized units and was far less high-tech compared to South Vietnam yet the South Vietnamese army seemed to almost completely collapsed in the face of the North Vietnamese army. Why did this happen?
South Vietnam had a lot of support in the form of money and weapons, but North Vietnam had a powerful revolutionary ideology. This ideology was a tool the state used to recruit dedicated soldiers who could fight and infiltrate into the south. This infiltration encouraged swaying people to “joining the fight.”
another thing i think really helped the north was the mountainous terrain. The Vietnamese soldiers learned how to retreat and plan in the mountains, where the south maintained on lowland!
To me this is a question of geography, economics, political ideology, and the unpredictability of bloody wars. There could never be one answer, but nonetheless, here are some things to consider