So the logic is everybody, whales included, votes in their best interest. Therefore, if you are holding a lot of Steem Power it is in your best interest to upvote quality content that you think will help the ecosystem obtain success and thus increase the value of your investment.

But what if you are a whale and you are of the opinion that steem/steemit is not likely to be a long term success? What is in your best interest then? Your investment is locked up in SP and you think it likely will lose most of its value regardless of your actions. If I were this hypothetical whale I would try to game the system to try to earn as many Steem Dollars as possible so that I could convert to steem and cash out.

This could be a possible reasons for whales doing things such as using bots to upvote content that may not do much to help steemit.