It was always somewhere around 80-90% people just gaming the system to maximize rewards, that's why the same 10 people have been the highest earners for a year now.
It's even built into the system itself: if you vote on a post early, and a bunch of whales up-vote it after you, then you get a huge amount of curation rewards. Thus, the more that a creator generally earns, the more that people are going to flock to their posts to get the benefits of the whale auto-votes they know are coming.
This is a little sad, as with time the site might not stay or become more popular. When new good users join, and they write great posts and then they get close to nothing, most of them will leave. What do you think a solution to this problem might be? Maybe put a cap per day/month per account? Or something else?