Modify users.php page to create page/post on button clicked

Use wp-admin/admin.php with an action parameter:

<a href="https://wordpress.stackexchange.com/questions/184153/<?php echo esc_url( admin_url("admin.php?action=wpse_184153_create_page&user_id=$user_id" ) ) ?>">Create Page</a>

And then hook onto the event:

function wpse_184153_create_page() {
    $redirect = admin_url( 'users.php' );

    if ( ! empty( $_GET['user_id'] ) && $user = get_userdata( ( int ) $_GET['user_id'] ) ) {
        // Create your page

        // Add any URL parameters you need for the return page
        $redirect = add_query_arg( 'created_page', $user->ID, $redirect );
    }

    // Send 'em back to users.php
    wp_redirect( $redirect );
    exit;
}

add_action( 'admin_action_wpse_184153_create_page', 'wpse_184153_create_page' );

You can name the function anything you want – the key thing to notice is how the hook matches the value of your action parameter, with the suffix admin_action_.