Probably the trust system weighs too much on trust and not enough on zaps. The contribution of a zap to an item's trust-weighted-score is: trust * log10(zap). This means that someone with half the trust will have to zap 10 times more to get the same effect as someone with double their trust.

There's also a heavy time decay as well. So your older post is going to be downweighted relative to newer posts.