Hello moon chu,
This is due to the table calculation partitioning in the view.
To fix, create a new calculated field set to ""
place the field on the marks shelf
Export to Excel.
This will now export three columns including a [Person] field from the Marks shelf. You could remove this after the fact.
One other option is to publish this to Tableau Server and then once it is published, add ".csv" to the URL of the view and a CSV will be created that contains 2 columns.
I hope this helps.