What can nextElementSibling do in Bootstrap Multi Slide Carousel

I thought el.nextElementSibling would select the next DIV with class "carousel-item" but after doing tests it appears as if el.nextElementSibling is simultaneously selecting all other DIVs on the page with class "carousel-item". I am just trying to get a better understanding of how the Bootstrap Multi Slide Carousel works.

JS

let items = document.querySelectorAll('.carousel .carousel-item')
items.forEach((el) => {

    const minPerSlide = 4
    let next = el.nextElementSibling
  
    for (var i=1; i<minPerSlide; i++) {
        if (!next) {
            console.log("no next")
            // wrap carousel by using first child
            next = items[0]
        }
        
        let cloneChild = next.cloneNode(true)
        el.appendChild(cloneChild.children[0])
        next = next.nextElementSibling


    }

   

})

HTML

<div class="container text-center my-3">
    <h2 class="font-weight-light">Bootstrap Multi Slide Carousel</h2>
    <div class="row mx-auto my-auto justify-content-center">
        <div id="recipeCarousel" class="carousel slide" data-bs-ride="carousel">
            <div class="carousel-inner" role="listbox">
                <div class="carousel-item active">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400/31f?text=1" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 1</div>
                        </div>
                    </div>
                </div>
                <div class="carousel-item">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400/e66?text=2" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 2</div>
                        </div>
                    </div>
                </div>
                <div class="carousel-item">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400/7d2?text=3" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 3</div>
                        </div>
                    </div>
                </div>
                <div class="carousel-item">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400?text=4" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 4</div>
                        </div>
                    </div>
                </div>
                <div class="carousel-item">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400/aba?text=5" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 5</div>
                        </div>
                    </div>
                </div>
                <div class="carousel-item">
                    <div class="col-md-3">
                        <div class="card">
                            <div class="card-img">
                                <img src="//via.placeholder.com/500x400/fc0?text=6" class="img-fluid">
                            </div>
                            <div class="card-img-overlay">Slide 6</div>
                        </div>
                    </div>
                </div>
            </div>
            <a class="carousel-control-prev bg-transparent w-aut" href="#recipeCarousel" role="button" data-bs-slide="prev">
                <span class="carousel-control-prev-icon" aria-hidden="true"></span>
            </a>
            <a class="carousel-control-next bg-transparent w-aut" href="#recipeCarousel" role="button" data-bs-slide="next">
                <span class="carousel-control-next-icon" aria-hidden="true"></span>
            </a>
        </div>
    </div>
    <h5 class="mt-2 fw-light">advances one slide at a time</h5>
</div>