---
- name: Using only loop keyword to iterate over list stored in another file
  hosts: nodes
  vars_files: /tmp/list.yml
  tasks:
    - name: Group adding
      group:
        name: "{{ item }}"
        state: present
      loop:
        - group1
        - group2
        - group3
    
    - name: User Adding
      user:
        name: "{{ item[0] }}"
        groups: "{{ item[1] }}"
        append: yes
      with_nested:
         - { Ram, Sham, Hanuman }
         - { group1, group2, group3 }
...