Apple ID locked - Being forced to change password
I don't even know how many years I've had my Apple ID but for the first time ever, when sitting down to start work, every one of my devices suddenly became unusable as I was informed that my Apple ID had been locked and required verification and then a new password before I was allowed to continue. My initial thought was that my account had been compromised. What would initiate an Apple ID lock leading to a password change being required?
MacBook Pro 13″, macOS 10.15