Code randomly choosing div class after else

I have my first half of the code which is supposed to be post with thumbnail in classes. One is class item a and other is class item b. But after "else" the code takes the same class item a even if I haven't put it around the code. Why does this happen?

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
  
  
    <div class="item a">
    <?php if( has_post_thumbnail() ): ?>
    
      
        <a href="<?php the_permalink()?>">
        <div class="thumbnail"><?php the_post_thumbnail('medium'); ?></div>
      </a>
      
  
      </div>
      
     <div class="item b">
      <?php the_title( sprintf('<h3 class="entry-title"><a href="%s">', esc_url( get_permalink() ) ),'</a></h3>' ); ?>
      
 
         <?php

    $content = get_the_content();
    $trimmed_content = wp_trim_words( $content, 33, NULL );
    echo $trimmed_content;


?>

</div>
    
    <?php else : ?>
    
          <?php the_title( sprintf('<h3 class="entry-title"><a href="%s">', esc_url( get_permalink() ) ),'</a></h3>' ); ?>
      
      <?php

    $content = get_the_content();
    $trimmed_content = wp_trim_words( $content, 33, NULL );
    echo $trimmed_content;

?>

    <?php endif; ?>
  

</article>

The first article is with thumbnail and other is without thumbnail on the image.