Sort Views table field by alphabet
Taxonomy term fields are entity reference fields. They only store the reference to the entity, which usually a number that is the ID for that entity. In case of Taxonomy the reference fields store the TID (taxonomy term ID) which is the number you can see in the path when you edit the term in the admin area. 

When you sort your table using the reference field, it will follow the number sort of the term IDs. 

But you want to sort alphabetically using term names. 

Term names aren't stored in node tables in the database, taxonomy module has its own tables. You have to pull the term data into your node views in order to use it as a sorting criteria. 

To pull related data into views use Relationships. 

In your case you have to add the Relationship for the Manufacturer taxonomy term field. After you add that Relationship you will be able to add a new field to your views called Taxonomy term: Name. You will be able to sort your table using that field, and the results will be sorted alphabetically! 

Remove your original Manufacturer field if you don't need it for anything else, the Term name field should be able to work as a full replacement while also providing the alphabetic sort criteria.