Apple ID hacked

See these security-related documents, especially the first two.

If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

Security and your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

Using app-specific passwords https://support.apple.com/en-us/HT204397

UseTwo-factor authentication for Apple ID https://support.apple.com/en-us/HT204915

You can also add 2 Factor Authentication to your account for more security. If the attempts continue, you might want to consider a name change.

Note the restrictions in the article.

Apple ID Name Change.        

 What to do after you change your Apple ID or password - Apple Support    I suggest doing this before you change your Apple ID or password.

Apple ID -Two-factor authentication          

 Two Factor Authentification availability.     

 Apple ID - Using app-specific passwords.     

Apple ID - Two Step Verifications FAQ