I am trying to add a default image to an image field in Drupal 8 using the configuration management interface (CMI). Normally once I have a field configured through the admin UI, I would then export the config YAML file for that field so I can add it to my custom module. The issue is that the default image for an image field is content and cannot be directly exported.

If I do export such a file, it would look like this:

langcode: en
status: true
dependencies:
  config:
    - field.storage.node.field_bluescope_header_bg_image
    - node.type.bluescope_page
  module:
    - image
id: node.bluescope_page.field_bluescope_header_bg_image
field_name: field_bluescope_header_bg_image
entity_type: node
bundle: bluescope_page
label: 'Header background image'
description: 'Image used as the page''s header background'
required: false
translatable: false
default_value: {  }
default_value_callback: ''
settings:
  file_directory: images/header-bg
  file_extensions: 'png gif jpg jpeg'
  max_filesize: ''
  max_resolution: ''
  min_resolution: ''
  alt_field: true
  alt_field_required: true
  title_field: false
  title_field_required: false
  default_image:
    uuid: 8288b3b1-4b0e-4efc-9137-55cb68382f0a
    alt: 'Header background image'
    title: ''
    width: 1920
    height: 1080
  handler: 'default:file'
  handler_settings: {  }
field_type: image

I noted that the default image is referred to using a uuid. I was thinking that I could address this by programmatically adding the default file to this field's configuration during the module install process. What I tried was to create the image in drupal's file system and then get the uuid of that file and add it to the fields configuration using configFactory:

function colorbond_data_install() {
  $config_factory = \Drupal::configFactory();
  $field_bluescope_header_bg_image_config = $config_factory->getEditable('field.field.node.bluescope_page.field_bluescope_header_bg_image');
  $default_image = $field_bluescope_header_bg_image_config->get('settings.default_image');

  // Create default image file.
  $file_info = colorbond_data_add_file('public://images/header-bg/', 'starwars.jpg', 'Header background image');
  $file = File::load($file_info['target_id']);

  $default_image['uuid'] = $file->uuid();
  $default_image['alt'] = 'Header background image';
  $default_image['title'] = 'Header background image';
  $default_image['height'] = 1080;
  $default_image['width'] = 1920; 
  
  $field_bluescope_header_bg_image_config->set('settings.default_image', $default_image);
  drupal_flush_all_caches();
}

The problem is that when I reinstall the module, the default image configuration does not appear:

Not sure what I am doing wrong.