Sarcasm done improperly isn't perceived as sarcasm, so it gets downvoted because your readers didn't get it. Happens fairly often. Maybe you've noticed.

Everyone isn't going to think "Hmmmmm, maybe this guy is trying to be funny but doesn't use sarcasm effectively, lemme check the comment history;" they just downvote and move on.

Sarcasm done improperly isn't perceived as sarcasm, so it gets downvoted because your readers didn't get it. Happens fairly often. Maybe you've noticed.