WordPress does not find author pages in search

I used this extra query in search.php:

$search_string = esc_attr( trim( get_query_var('s') ) );
$wp_user_query = new WP_User_Query( array(
'meta_query' => array(
    'relation' => 'OR',
    array(
        'key'     => 'first_name',
        'value'   => $search_string,
        'compare' => 'LIKE'
    ),
    array(
        'key'     => 'last_name',
        'value'   => $search_string,
        'compare' => 'LIKE'
    )
)
) );

With a custom loop:

<?php
// Get the results
$authors = $wp_user_query->get_results();
// Check for results
if ( ! empty( $authors ) ) { ?>
  <?php foreach ( $authors as $author ) {
  // get all the user's data
  $author_info = get_userdata( $author->ID );
  ?>
    <article class="post">
      <header class="entry-header">
        <h1 class="entry-title"><?php echo $author_info->display_name; ?></h1>
      </header>
      <div class="entry-content">
        <p><?php echo wp_trim_words( get_the_author_meta('description',$author_info->ID), 50, '...' ); ?></p>
        <a href="https://wordpress.stackexchange.com/author/<?php echo $author_info->user_nicename; ?>" class="arrowafter">Lees verder</a>
      </div>
    </article>
  <?php } ?>
<?php } ?>