Why would you this wasn't even a hack for my understanding?

It was a password stuffing attack. Meaning that a bunch of users with reused crappy passwords had their accounts accessed with their legitimate passwords by attackers.

I'm not sure why this reflects horribly on the company in a way that would encourage one to delete their account?

This would be like leaving the key to your apartment in a public place and then complaining about your landlords terrible security when someone accesses your house when you're not there.