There can be some reasons why you want to reinstall wordpress multisite (network). For example, you decide to change it from sub-domain to sub-directory. Even if you remove all entries from wp-config.php file, it won’t let you reinstall network and will write: “Warning: An existing WordPress network was detected.“.
To remove this message, you have to delete these tables from database (after removing everything from config file):
That’s it, now you can start installing WordPress network (Multisite) as if it was never installed before :)