The order and timing matter a lot because the weight of each (down)zap decays exponentially.
Oftentimes, the posts you're talking about were visible for hours because of the zaps they received. Then they received the downzaps and got knocked down. In this case, you're ignoring the initial hours of visibilty.
Other times (and often because you draw attention to it), posts that were downzapped out of visibility receive new zaps. Because this happens hours after the downzap, the new zaps significantly outweigh the downzap and the post becomes Lit again.
The order and timing matter a lot because the weight of each (down)zap decays exponentially.
Oftentimes, the posts you're talking about were visible for hours because of the zaps they received. Then they received the downzaps and got knocked down. In this case, you're ignoring the initial hours of visibilty.
Other times (and often because you draw attention to it), posts that were downzapped out of visibility receive new zaps. Because this happens hours after the downzap, the new zaps significantly outweigh the downzap and the post becomes Lit again.