Generating User(s) with Settings API

I am trying to create a plugin that will generate users. I am pretty new to WordPress and my PHP is ehhhh. The idea for it is for the plugin to generate multiple users when its finished. Right now though I am just trying to get it to generate one. But I am having issues trying to do so, any ideas?

Once I click Submit, I get a ‘Settings Saved’. So, I believe that means the form went through but no user shows up in the DB. I imagine I am not getting the information in the form or executing my function properly.

<?php
function sl_add_options_page() {
    // Add new page under the "Settings tab
    add_options_page(
        __( 'User Options' ),
        __( 'User Options' ),
        'manage_options',
        'user_options_page',
        'sl_render_options_page'
    );
}

add_action( 'admin_menu', 'sl_add_options_page' );

function sl_render_options_page() {
    ?>
    <div class="wrap">
        <h2><?php _e( 'Content & User Generator Options' ); ?></h2>
        <form action="options.php" method="post">
            <?php settings_fields( 'num_users' ); ?>
            <?php do_settings_sections( 'user_options_page' ); ?>
            <p class="submit">
                <input type="submit" name="submit" id="submit" class="button button-primary" value="<?php _e( 'Submit' ); ?>">
            </p>
        </form>
    </div>
    <?php
}

function sl_add_setting() {
    // Register a binary value called "pimple_disable"
    register_setting(
        'num_users',
        'num_users',
        'absint'
    );

    // Add the settings section to hold the interface
    add_settings_section(
        'user_main_settings',
        __( 'User Controls' ),
        'sl_render_main_settings_section',
        'user_options_page'
    );

    // Add the settings field to define the interface
    add_settings_field(
        'user_main_settings_field',
        __( 'How Many users' ),
        'sl_render_users_input',
        'user_options_page',
        'user_main_settings',
        'sl_wp_create_user'
    );
}

add_action( 'admin_init', 'sl_add_setting' );

function sl_wp_create_user($username, $password, $email) {
    $num_users = intval( $_GET['num_users'] );
    $username = 'Testing';
    $email = 'fakeemail@easyfakemail.com';
    $password = wp_generate_password( 12, false );

    for( $j = 0; $j < $num_users; $j++ ) { 

        $user_login = esc_sql( $username );
        $user_email = esc_sql( $email    );
        $user_pass = $password;

        $userdata = compact('user_login', 'user_email', 'user_pass');
        return wp_insert_user($userdata);
    }

    echo '<div id="message" class="updated fade"><p><strong>' . $num_users . ' Users created</strong></p></div>';
}

function sl_render_main_settings_section() {
    echo '<p>Main settings for the Content and User Generator plugin.</p>';
}

function sl_render_users_input() {
    echo '<input id="num_users" name="num_users" type="input" value=""  />';
}