There wasn't quite any sort of intended playstyle. My own playstyle was trying to scatter my defenses around slowly so any monsters would usually be within range of a correctly armed villager before they killed too many humans.
There isn't a set limit to the number of villagers or forces game over from that, so that might just be a bug. I'll probably have to make a bigger trade-off for those cards so you can't survive forever like that. That one is meant to be repeatable though, sorta as a reward after surviving so long, though I would have expected someone to choose the Reset option at some point.
Thank you for giving it a shot!