Sure, people should lose their job because someone's diagnosing a network problem, happens to run tcpdump on a server behind a TLS-terminating load balancer, and sees username/passwords. /s This literally happens all the time.
If that isn't what happened, someone should be losing their job. The minute you think diagnosing network problems is a reason to ignore security to a degree that your users need to be notified you're incompetent.
If they just left a log or capture file around somewhere, nope. Everyone makes mistakes.
I guess that's where you and I differ. There are certain mistakes that are tolerable. But ones that result in mass emailing to your clients that they need to change their passwords are not. I'd never heard of robinhood.com before, but now I have, and my impression is I'd never trust them because they have staff that makes mistakes with my secure information.
Think of how robinhood.com's employees feel about this. Management, and the people who are now watching the fallout rob the company of revenue.
Telling me that the person who made that mistake is gone might make me think differently.
The minute you start taking users name and passwords you're in the big boy world and need to treat it as such. Mistakes can be fatal, not just for your job, but your company.
Some organizations would simply ignore this and move on. You'd never know it even happened.
https://www.zdnet.com/article/github-says-bug-exposed-accoun...
https://arstechnica.com/information-technology/2018/05/twitt...
https://www.theverge.com/2019/3/21/18275837/facebook-plain-t...
Just my 2 c
Also, there are zero-knowledge authentication systems, but they are somewhat iterative due to their probabilistic nature. They are secure in the face of an imposter authentication service, as the password (or a hash, obviously) has to be stored in the real authentication service. But it is never transmitted after this initial store, so no amount of logging or posing as an evil imposter risks disclosure.