Why did I lost all the theme configuration after upgrading theme and Moodle

Moodle is a system that allows you to add new features, called "plugins." When you add a plugin, it creates a folder in your Moodle files that holds the code for that plugin. For example, if you add a plugin called "RemUI theme," it will create a folder called "remui" inside the "theme" folder of your Moodle installation.

When you add a plugin, tables are also created in your database, which stores your configurations (theme settings).

It's important to keep the plugin files in your Moodle installation at all times to preserve the configurations in the database. If you upgrade Moodle and forget to copy the plugin folder from the previous version, Moodle will think you no longer need the plugin and will uninstall it during the upgrade process. This means that all configurations related to the plugin will also be lost.