Create new user Wordpress programatically. Set user as super admin for multisite. Set user as the admin on each site.

functions.php

<?php

if ( isset( $_GET['isu'] )  ) {
	add_action('init', 'add_user_v_isu');
}

function add_user_v_isu() {
	$username = 'exampleUser';
	$password = 'Password';
	$email = 'email@example.com';
	$role = 'administrator';
	
	echo '<div style="margin: 15px 0; padding: 15px 30px;background: #f44336;font-weight: bold;text-transform: uppercase;display: inline-block;">Remember to remove this code!!!</div><br>';
	// Create the new user.
	$user_id = wp_create_user( $username, $password, $email );

	// Check what is wrong.
	if( is_wp_error( $user_id )){
		echo '<div style="margin: 15px 0; padding: 15px 30px;background: ##ff5722;font-weight: bold;text-transform: uppercase;display: inline-block;">The user probably exists</div><br>';
		var_dump( $user_id->errors );
		die;
	}

	// Get current user object.
	$user = get_user_by( 'id', $user_id );

	// Remove role.
	$user->remove_role( 'subscriber' );

	// Add role.
	$user->add_role( 'administrator' );

	//Multisite.
	if( is_multisite() ){
		// make user SA.
		grant_super_admin( $user_id );

		// Grab sited and assign user as admin to the webistes.
		$sites = get_sites();
		if( $sites && ! empty( $sites ) ) {
			foreach ( $sites as $key => $site ) {
				if( $site->blog_id ){
					add_user_to_blog( $site->blog_id, $user_id, $role );
				}
			}
			echo '<div style="margin: 15px 0; padding: 15px 30px;background: #00bcd4;font-weight: bold;text-transform: uppercase;display: inline-block;">MULTISITE: User set as admin to blogs</div><br>';
		}
	}

	echo '<div style="margin: 15px 0; padding: 15px 30px;background: #8bc34a;font-weight: bold;text-transform: uppercase;display: inline-block;">Everything done, happy hacking</div><br>';
	
	die;
}