In addition to the obvious conflict of interest in relations with advertisers which is the focus of this story, this also implies it would be in Facebook's interests to go easy on fake accounts and tolerate their existence. That's troubling, and just in itself it appears contrary to their public facing policy
Why? Wouldn't the people working on fake accounts only care about their own metrics? How would it affect them if some other team's metrics are affected?
There may be clickfarms that have their interests (accidentally) aligned with FB's in specific cases, which would mean FB has no interest in cracking down on them. And I wouldn't put it past FB to even indirectly operate such clickfarms if this means they can offer some support for the overinflated promises they make to advertisers.
You misunderstand me. You speak of Facebook as a large amorphous blob. But think of it in terms of people working on these problems. Why should the fake accounts team care about the metrics of the ads team? They will be rewarded based number of fake accounts caught, presumably. Not ad spend. So why would they not do their jobs?
So, the fake accounts team does its job and identifies a huge group of accounts that it alleges are fake. It goes up the chain and nope, we won't shut them down, this isn't clear-cut, we need more evidence, etc.