The purpose of an armed populace isn't to "win" tactically, it's to win strategically and psychologically. It's basically like a poison pill clause, you want to make totalitarian takeover so unpallatable that every victory is a pyrrhic one. You want to force the occupiers to have to choose between killing your own countrymen or defecting, setting up more of a resistance. All the while, you shine light on all the atrocities.
With a sparsely-armed populace, it's easy for the occupying force to roll through without much conflict or challenging decisions.
Winning occurs through attrition of the occupiers, which, unlike Vietnam, can't just "back out".