How do I make my youtube videos appear with fast site loading?

Question

I restate my question here: When I work on a test page of my site (https://www.jobcool.fr/single.html), the youtube videos appear but when I put this page on the internet with filezilla, the videos no longer work. I used a code that can lighten the weight of youtube videos

<script>
  ( function() {

    var youtube = document.querySelectorAll( ".youtube" );

    for (var i = 0; i < youtube.length; i++) {
      
      var source = "https://img.youtube.com/vi/"+ youtube[i].dataset.embed +"/sddefault.jpg";
      
      var image = new Image();
          image.src = source;
          image.addEventListener( "load", function() {
            youtube[ i ].appendChild( image );
          }( i ) );
      
          youtube[i].addEventListener( "click", function() {

            var iframe = document.createElement( "iframe" );

                iframe.setAttribute( "frameborder", "0" );
                iframe.setAttribute( "allowfullscreen", "" );
                iframe.setAttribute( "src", "https://www.youtube.com/embed/"+ this.dataset.embed +"?rel=0&showinfo=0&autoplay=1" );

                this.innerHTML = "";
                this.appendChild( iframe );
          } );  
    };

    } )();
</script> 

/*=======VIDEO YOUTUBE=======*/

.video .youtube {
    background-color: #000;
    position: relative;
    padding-top: 56.25%;
    overflow: hidden;
    cursor: pointer;
}
.youtube img {
    width: 100%;
    top: -16.82%;
    left: 0;
    opacity: 0.7;
}
.youtube .play-button {
    width: 90px;
    height: 60px;
    background-color: #333;
    box-shadow: 0 0 30px rgba( 0,0,0,0.6 );
    z-index: 1;
    opacity: 0.8;
    border-radius: 6px;
}
.youtube .play-button:before {
    content: "";
    border-style: solid;
    border-width: 15px 0 15px 26.0px;
    border-color: transparent transparent transparent #fff;
}
.youtube img,
.youtube .play-button {
    cursor: pointer;
}
.youtube img,
.youtube iframe,
.youtube .play-button,
.youtube .play-button:before {
    position: absolute;
}
.youtube .play-button,
.youtube .play-button:before {
    top: 50%;
    left: 50%;
    transform: translate3d( -50%, -50%, 0 );
}
.youtube iframe {
    height: 100%;
    width: 100%;
    top: 0;
    left: 0;
}
.video {
    display: block;
    width: 600px;
    margin: 0 auto 35px auto;
    max-width: 100%;
}
/*=======CADRE DE LA VIDEO YOUTUBE=======*/
.video .wrapper {
    border: 5px solid black;
    width: 100%;
}
/*=======CADRE DE LA VIDEO=======*/
.video .wrapper {
    width: 100%;
    padding: 7.5px 7.5px;
    border: 1px solid #C9C9C9;
    -webkit-box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19),
    0 6px 6px rgba(0, 0, 0, 0.23);
    -moz-box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19),
    0 6px 6px rgba(0, 0, 0, 0.23);
    -ms-box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19),
    0 6px 6px rgba(0, 0, 0, 0.23);
    -o-box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19),
    0 6px 6px rgba(0, 0, 0, 0.23);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19),
    0 6px 6px rgba(0, 0, 0, 0.23);
}
.video .wrapper {
    -webkit-transform: rotate(-2deg);
    -moz-transform: rotate(-2deg);
}
/* Rotate all even images 2 degrees */
.video .wrapper:nth-child(even) a img {
    -webkit-transform: rotate(2deg);
    -moz-transform: rotate(2deg);
}
/* Don't rotate every third image, but offset its position */
.video .wrapper:nth-child(3n) a img {
    -webkit-transform: none;
    -moz-transform: none;
    position: relative;
    top: -5px;
}
/* Rotate every fifth image by 5 degrees and offset it */
.video .wrapper:nth-child(5n) a img {
    -webkit-transform: rotate(5deg);
    -moz-transform: rotate(5deg);
    position: relative;
    right: 5px;
}
/* Keep default rotate for every eighth, but offset it */
.video .wrapper:nth-child(8n) a img {
    position: relative;
    top: 8px;
    right: 5px;
}
/* Keep default rotate for every eleventh, but offset it */
.video .wrapper:nth-child(11n) a img {
    position: relative;
    top: 3px;
    left: -5px;
}
.video .wrapper:hover {
    -webkit-transform: scale(1.25);
    -moz-transform: scale(1.25);
    position: relative;
    z-index: 5;
}
.video .wrapper {
    -webkit-transition: -webkit-transform .15s linear;
    -webkit-box-shadow: 0 3px 6px rgba(0, 0, 0, .25);
    -moz-box-shadow: 0 3px 6px rgba(0, 0, 0, .25);
}
/* On hover, darken the shadows a bit */
.video .wrapper {
    -webkit-box-shadow: 0 3px 6px rgba(white);
    -moz-box-shadow: 0 3px 6px rgba(white);
}

<div class="video" data-id="abn-w2Gs54o">
    <div class="wrapper">
        <div class="youtube" data-embed="abn-w2Gs54o">
            <div class="play-button"></div>
        </div>
    </div>
</div>

Could you help me understand why? Best regards enter image description here