JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="list_1">
  <li class="list_1_items">
    <a href="">Элемент 1</a>
    <ul class="list_2">
      <li class="list_2_items"><a href="">Элемент 1_1</a></li>
		  <li class="list_2_items"><a href="">Элемент 1_2</a></li>
    </ul>
  </li>
   <li class="list_1_items">
    <a href="">Элемент 2</a>
    <ul class="list_2">
      <li class="list_2_items"><a href="">Элемент 2_1</a></li>
		  <li class="list_2_items"><a href="">Элемент 2_2</a></li>
    </ul>
  </li>
 </ul>

CSS

.list_2 {
  	display: none;
}


.list_1 li:hover .list_2 {
  	display: block
}