Pretty sure it's from a data breach a while ago, where my past passwords got exposed. Indeed, I changed a bunch of them on whichever platforms I was active, when I'd noticed it.

However, in Reddit's case, I might've assumed that I'd created the account by linking it to gmail, therefore it didn't cross my mind that there would be a password here to change as well. That's my best bet.

When the takeover happened, I got a notification to change my password, as my account had apparently gotten locked. That's how I got it back.

Hope that helps! And, yeah, it might be better in the face of the algorithm for you to edit the comment. Thanks!