Hello,
It appears that the hackers removed your email address (alias) from your Microsoft account and replaced it with their own.
If it is a @gmail.com address associated with your Microsoft account, this email address (Alias) can be associated with another Microsoft account again. However, the account with all the data and purchases cannot be recovered.
In this situation, you can contact the Xbox Account Recovery team, which handles compromised accounts even if the email address has been changed. Be sure to provide all required details accurately when you submit the form.
Recover your Microsoft account
To help prevent this from happening, Microsoft always recommends protecting your account with a strong, unique password and enabling two-factor authentication. This adds an extra layer of security because, even if someone knows your password, they would still need a second verification method, such as a security code or the Microsoft Authenticator app, to sign in.