How to link user taxonomy-term to a list with all users with that term applied?
First of all, I assume that the views module is installed and both the views and views_ui modules are enabled.

In the views admin page (/admin/structure/views), there is a view Taxonomy term. If you click edit to see the view settings, you will see that the view is only configured to show Content (i.e. nodes of a content type).

Off hand, I am not sure how to configure the Taxonomy term view to also show Users.  Anyway, I would not take this approach.

My suggestion is to:

Step 1) In the manage display screen for the User fields (/admin/config/people/accounts/display), set the display of your term field to Hidden.

Step 2) Add a new view page display that lists users associated with a term.  You need to use a Contextual filter on the term id (TID).

Step 3) Add a new view block display to lists terms associated with a User.  You need to use a Contextual filter on the user id (UID), so that only the terms related to the user are displayed. For the term field, Rewrite the output so that it is formatted as a link to the aforementioned view page (Step 2) and passing the TID as an argument.

Step 4) Display the view block on the user page such that it appears in a region below the user fields.

This is somewhat involved, but should work.

You may also want to take a look at the module https://www.drupal.org/project/taxonomy_display. This module may open up some other options.