How to delete users from the server?
You can delete a user from Tableau Server only if the user does not own any content (projects, workbooks, views, or data sources). If you attempt to delete a user who owns content, the user site role will be set to Unlicensed, but the user will not be deleted.
If a user is a member of multiple sites, and owns content in one or more of those sites, the user will be removed from the sites in which they don’t own content. The user will remain a member in sites where they do own content, but demoted to the Unlicensed site role.
In the site menu, click Manage All Sites, and then click Users. In a single-site environment, click Users.
Select one or more users to delete, and then click Actions > Delete.
Click Delete in the confirmation dialog box.