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.