Reassign $view_mode using entity field passed to hook_entity_view_mode_alter()
I'm not sure exactly what's going on here, but looking at the documentation for hook_view_mode_alter, it looks like you're not resetting the view mode properly. It looks like you need to set it like:

/**
 * Implements hook_entity_view_mode_alter().        
 */
function nfl_entity_view_mode_alter(&amp;$view_mode, Drupal\Core\Entity\EntityInterface $entity, $context) {
  // Change the view mode to the value selected via radio button on the form.
  if ($entity-&gt;getEntityTypeId() == 'nfl_fact' ) {
    $view_mode = $entity-&gt;change_view-&gt;value;
  }
}