Why my Ajax events are no longer detected after dynamic change of shortcode content

I found the solution, I had to do the right ajax actions…
For the second dropdown, I had to first detect the click on the statically created div then detect the change on the dynamically created dropdown.

Here the correct code:

<?php 
/**
 *   Plugin Name: demoConnecteurs
 *   Description: Plugin de démo des connecteurs Jenkins et Mantis
**/
require_once(file_with_external_fonctions.php);

$inst_demo = new demo();
if (isset($inst_demo)){
}

class demo{   
    private $dataFirstDropdown;
    private $dataSecondDropdown;
    private $dataDependingSecondDropdown;


    function __construct(){
        $this->setDataFirstDropdown();

        $this->initAjaxActions();

        add_action('admin_enqueue_scripts', array($this,'demo_scripts'));
        add_action('wp_enqueue_scripts', array($this,'demo_scripts'));


        $this->init();
    }

    function initAjaxActions(){
        add_action('wp_ajax_setChoiceFirstDropdown', array($this,'setChoiceFirstDropdown'));
        add_action('wp_ajax_nopriv_setChoiceFirstDropdown', array($this,'setChoiceFirstDropdown'));        
        add_action('wp_ajax_setChoiceSecondDropdown', array($this,'setChoiceSecondDropdown'));
        add_action('wp_ajax_nopriv_setChoiceSecondDropdown', array($this,'setChoiceSecondDropdown'));
    }

    function demo_scripts(){
        wp_register_script( 'ajaxHandle', plugins_url() . '/DemoConnecteurs/buttons_ajax.js');
        wp_localize_script( 'ajaxHandle', 'ajax_object', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );

        wp_enqueue_script( 'ajaxHandle');
    }

    function init(){
        add_shortcode( 'demo', array($this,'demo_shortcode') );
    }

    function demo_shortcode () {
        return $this->contentCore();
    }

    public function setDataFirstDropdown(){
        $this->dataFirstDropdown = getDataFirstDropdown(); //external function
    }

   public function setDataSecondDropdown(){
        $this->dataSecondDropdown = getDataSecondDropdown($this->dataFirstDropdown); //external function
    }

   public function setDataDependingSecondDropdown(){
        $this->dataResultsOfSecondDropdown = getDataDependingSecondDropdown($this->dataSecondDropdown);
    }

    public function setChoiceFirstDropdown(){
        if (isset ($_POST['demo_data_first_dropdown']))$this->dataFirstDropdown = $_POST['demo_data_first_dropdown'];

        $this->setDataSecondDropdown();
        echo $this->contentSecondDropdown();
        wp_die();
    }

    public function setChoiceSecondDropdown(){
        if (isset ($_POST['demo_data_second_dropdown']))$this->dataDependingSecondDropdown = $_POST['demo_data_second_dropdown'];

        $this->setDataDependingSecondDropdown();
        echo $this->contentDependingSecondDropdown();
        wp_die();
    }

    function contentCore(){
        $html = "";

        $html .= '<div id="firstDropdown" : ';        
        $html .= '<select id="selectFirstDropdown">';
        foreach($this->dataFirstDropdown as $f) {
           //working
        }
        $html .= '</select></div>';

        $html .= '<div id="secondDropdown"></div>';

        $html .= '<div id="dependingSecondDropdown"></div>';

        return $html;
    }

    public function contentSecondDropdown(){
        $html="<select id="selectSecondDropdown">";
        foreach($this->dataSecondDropdown as $s) {
           //working
        }
        $html .= '</select></div>';
        return $html;
    }

    public function contentDependingSecondDropdown(){
        $this->dataDependingSecondDropdown;
        return $html;
    }
}

jQuery(document).ready(function($) {

    $('#selectFirstDropdown').on('change', function (e) {
        jQuery.ajax({
            type: "POST",
            url: ajax_object.ajaxurl,
            data: {
                'action': 'setChoiceFirstDropdown',
                'demo_projet_name': $('#firstDropdown option:selected').val()
            },
            success: function (output) {
                $('#secondDropdown').html(output);
            }
        });
    } );

    $('#secondDropdown').on('click', function (e) {
        $('#selectSecondDropdown').on('click', function (e) {
                jQuery.ajax({
                type: "POST",
                url: ajax_object.ajaxurl,
                data: {
                    'action': 'setChoiceSecondDropdown',
                    'demo_version_id': $('#secondDropdown option:selected').val()
                },
                success: function (output) {
                    console.log(output);
                    $('#dependingSecondDropdown').html(output);
                }
            } );
        } );
    } );    
} );