Can't show author when using post field advanced

Hi Metabox,

Can you let me know why my code is not working? The other post details are showing except for this author name. I tried the get_the_author_meta but the output is incorrect. Any help?

Views

<div class="p2-post-related">	
	{% for item in post.related_post_single_product %}
	
		<div class="p2-post-related__card p2-post-related__card--centered">
			<img src="{{ item.thumbnail.full.url }}" width="{{ item.thumbnail.full.width }}" height="{{ item.thumbnail.full.height }}" alt="{{ item.thumbnail.full.alt }}">
			<div class="p2-post-related__wrapper">
				<h2 class="p2-post-related__header">
					<h3 class="p2-post-related__category">{{ mb.get_the_term_list( item.ID, 'category', '', ', ' ) }}</h3>
					<a href="{{ item.url }}" class="p2-post-related__title">{{ item.title }}</a>
				</h2>
				<div class="p2-post-related__meta">
					<div class="p2-post-related_author_name">by <a href="#">{{ mb.get_the_author_meta('nickname', author.ID) }} {{ mb.get_the_author_meta('last_name', author.ID) }}</a></div>	
				</div>
			</div>
		</div>
		<!-- p2-post-related__card -->
	{% endfor %}
</div>

The custom field

<?php
add_filter( 'rwmb_meta_boxes', 'your_prefix_function_name' );

function your_prefix_function_name( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = [
        'title'      => __( 'Add Related Post', 'your-text-domain' ),
        'id'         => 'related-post-single-product',
        'post_types' => ['product'],
        'fields'     => [
            [
                'name'       => __( 'Post', 'your-text-domain' ),
                'id'         => $prefix . 'related_post_single_product',
                'type'       => 'post',
                'post_type'  => ['post'],
                'field_type' => 'select_advanced',
                'multiple'   => true,
            ],
        ],
    ];

    return $meta_boxes;
}