The reason the trending section is so predictable is that certain authors are surrounded by cliques. Some of these authors, whose every post is sure to trend, let their 'in group' know exactly when they're going to drop a post, because by timing their votes, that group can substantially capture the rewards for curation of a trending post.
In return the favored author accrues huge financial gain from their posts. Both parties win - but as you point out, Steemit loses.
Even without the timing scheme, just piling on to a trending post provides rewards, and high visibility, which is important to gain followers that like what you have to say.
Hopefully it will sort itself out....it's nausea inducing and at an all time high lately. I've been here 11 months and been active daily. Thank you for your reply.