Not the trending content, but the trendy content. Like the steemit tags and the celebrity posters and whatnot. When the crowd knows what the trendy topics are, they're going to go vote them, even preemptively in the hopes that they'll be rewarded. The whales can change what is trending and what tends to be trendy by bucking it and finding quality.
Like I said - the very purpose of the whales is to curate quality; to reward those who deliver on quality content to make the platform more viable for the long-term. I'm not really seeing much of that. If there aren't enough whales to do that, then that's also a problem. But the incentive for curating tends to be skewing the trends and even influencing whale votes while they're missing out on far too much other quality. Dolphins seem to be helping, but the same curating incentive appears to be creating similar trends.
I don't know what the solution is, but if the voting habits continue, the quality will suffer at the expense of the entire platform - which, in turn, doesn't exactly benefit the whales. So it's on them to figure out a way to resolve the issues.