Below is from drupal.org

The hook will only be called the first time a module is enabled or after it is re-enabled after being uninstalled.

Generally, the “uninstalled” can be ignored. On the module page, there is a tag named “uninstall” on the top-right corner. Click to open, then the modules are listed there. check the space before the module you want to uninstall, then click “uninstall” button to uninstall.