Enable all languages for multilingual site I notice I can add languages one by one on this page
mysite.com/admin/config/regional/language/add

Is there an easy way for adding all languages?
Maybe there is a command with drush?
No - there is no drush command for this and you would want to do this one by one because you're going to need to upload your specific po translation files from Drupal.org (one reason its not practical to make this an option with the base install for n languages)