Not Allowed to Create User with GRANT
You needn't include the IDENTIFIED BY bit when granting privileges. If you need to create a user and grant permissions, that's two operations:
mysql> CREATE USER 'wordpress'@'localhost' IDENTIFIED WITH mysql_native_password BY '{superSecretPassword!123}';
mysql> GRANT ALL ON `wordpress`.* TO 'wordpress'@'localhost';
Be sure to change the superSecretPassword!123 bit to something better.