The passwords in plaintext wasn't a breach or a leak. If you punish Facebook for it, they would be less inclined to share such information in the future.
What's to stop a malicious ex-lover from grabbing a FB password and reading that person's private messages? If FB didn't even know there were passwords in plaintext, they very likely weren't auditing log access as much as was needed.
[1] https://www.theverge.com/2019/3/21/18275837/facebook-plain-t...