How to show a list of users subscribed to the current node's taxonomy terms
You can set the same vocabulary for users and your content type, so they will be related with the same terms, then you will be able to achieve your goal with these four steps:

#1

Create a View block with these settings:

View->name: Related users
Show -> taxonomy terms -> of type -> your vocabulary

#2

Create relationship:  Taxonomy term: User using [field_name] 

* field_name: the name of the field with term reference in users account settings

check: Require this relationship

#3

Add field: (field_name) User: Name 

* field_name: the name of the field with term reference in users account settings

#4

Add contextual filter: Taxonomy term: Term ID

Configure the contextual settings:

WHEN THE FILTER VALUE IS NOT AVAILABLE:

provide default value: taxonomy term id from URL

check: Load default filter from term page 

check:  Load default filter from node page,  that's good for related taxonomy blocks 

Select your vocabulary

Check: Filter to items that share any term 

WHEN THE FILTER VALUE IS AVAILABLE OR A DEFAULT IS PROVIDED:

Specify validation criteria -> basic validation

Action to take if filter value does not validate -> hide view

MORE:

check: Allow multiple values



That's all. If the current node will have a relation with some user or users, then the block with the related users will be displayed.