You are mistaken to some degree. It wasn't a single whale's vote that cost Jeff the money. Rather it was a very large number of them. His post was downvoted a total of like...47 times, many of them by whales.

And yet, even then it still managed to earn over $100, which is far more than the average post here on Steemit earns.

In short, no single "cop whale" can deprive a poster of tons of money. Only many whales acting together can make a post worth thousands, or subsequently deprive the post of thousands.