The solution to fake news and fake accounts is not as hard as claimed
Since algorithms clearly aren't remotely good enough to spot fake news, scams and fake accounts on Facebook, it is clear that actual people need to be hired to do this.
Facebook can afford to do this.
Zuck is probably concerned that the cost of employing people to do this on a long term basis will reduce profitability too much.
But hiring an army of people to do this will have a rapid impact on those who are currently abusing the weaknesses and loopholes in FB. It won't be as easy to adapt their activities to fool people as it has been to fool algorithms.
This will make it too hard for most abusers to keep going because they need a broad reach and low cost to achieve their goals. They can't be as confident they will succeed in that environment.
This will have the effect of driving them to other platforms where policing|moderating is weaker e.g. Twitter. The cost of human oversight for FB then falls, and FB have a lot more examples to feed their AI to create Zuck's dream solution of automated moderation (if that is actually possible).
Employing lots of people might also be good for FB PR, unless Zuck's zeal to eliminate jobs is too strong!
If a competitor does it first, the dodgy operators will move their activities to other platforms e.g. Facebook, making their current problems worse.