Accounts are locked for a number of reasons. Most frequently when a password has been entered incorrectly too many times and there is not sufficient information available to unlock the account. For the Apple Account, there are many security measures along with Two Factor Authentication indicating Trusted Device and Trusted Phone Number and also a Recovery Contact that can be added to the account that if previously enabled can be used to unlock the account. Accounts are also locked for a violation of the Terms of Use, and for those cases, there is no arbitration and can certainly happen without notification of violation or explanation of the violation.
In any case, if it is determined that the account cannot be unlocked, the only option is to create a new Apple Account.