Downvote power was never suppose to be so concentrated into such a small amount of accounts for downvoting.

No, but without the EIP incentives, people wouldn't downvote at all, as we saw for the first three and a half years. However, most people use their downvotes in a very narrow area, whereas Steemcleaners seek out the abuse that is designed to hide out of sight from the normal users. While people want the reward pool to go to real contributors, including themselves, most people aren't interested fighting the abuse themselves. You for example flagged this post for whatever reason you chose to, instead of looking for plagiarism - This is the behavior of the average person.