These were accounts that shouldn't have had console access in the first place, and were never used by humans to log in AFAICT. I don't know exactly what they were originally for, but they were named like "foo-robots", were very old.

At first I thought maybe some previous dev had set passwords for troubleshooting, saved those passwords in a password manager, and then got owned all these years later. But that's really, really, unlikely. And the timing is so curious.