From what I understand, upvotes are more influential/valuable from accounts that have greater Steem Power. So, if you cash out your Steem Power your influence decreases. All it takes is for a "whale" to upvote one of your posts, and if other whales notice, and also upvote, then it starts trending.

... don't know if this is totally accurate, I'm learning about this thing as I go along, too.