Password breach ??

If you mean Settings > Passwords. Yes, Apple posts information under Security Recommendations to detect compromised password (which you can also turn off). This matches your information (on device) against know data leaks so that you can change you password to better secure your account.

Yes. It's not out of the blue; just an accumulation of data breaches from companies for years. Most of us don't even know about them or never did anything to change credentials. And, a lot of us reuse usernames and passwords. Right now, I have 226 recommendations that include companies with data breaches and 50+ password recommendations for reused passwords (granted some of those are unavoidable if companies have multiple domains that use the same credentials).

From where did you get this message?