How can I programmatically import configuration?
You should save the config like $config_storage-&gt;save(); :
As @4K4 mentioned :


  The important thing is not simply store config, but create and save config entities and so run CRUD methods/hooks like https://api.drupal.org/api/drupal/core%21modules%21field%21src%21Entity%21FieldStorageConfig.php/function/FieldStorageConfig%3A%3ApreSave/8.7.x