You forgot one possible explanation; followers that just want to curate ... although you might think they'll be the first to vote ... because of the 30 minute limit, they will look at posts that are at least 15 minutes old, and based on whatever parameter they prefer to rely on ... take a gamble ... or not

point being; those curators follow hundreds of people, combined with the fact that after 20 votes the weight drops, which is why they're actually not voting on that many posts, they try to pick the 20 very best posts of that day, which is not much compared with the thousands of posts that are being created