I think it comes from people voting without clicking into the post.
I must admit I do it from time to time, when I see a post title that I think will do well but I don't have interest in reading.
Also a lot of people have multi accounts so only 1 would view it the rest would vote with looking
I mostly only vote on posts I read, but I don't expect to make much from curation anyway. I know some votes come from bots.