I recently saw a post asking why something that appeared to be a random string of characters was a bad password. One of the answers was that it already exists on a website so you can Google it by just searching the password.
More recently, I found out about Have I Been Pwned which has a database of user information that has been breached in the past. On its page about passwords, I noticed the same thing that the person said on StackExchange:
This exposure makes them unsuitable for ongoing use as they're at much greater risk of being used to take over other accounts.
Why does the password existing online make it unsafe? If I uploaded an infinitely large text file containing every password possible, would that make all passwords unsafe?