Getting the current author (it has changed) of a post, not the original author

Question

Your issue is your foreach loop. Because you don’t manually setup postdata, the current post object is not available in global scope, that is why you cannot make use of template tags or anything else for that matter that relies on the post object.

For get_the_author_meta() to work in your current situation, you will have to explicitely pass the current post author to the function. Something like this will work

get_the_author_meta( 'ID', $item->post_author );

To avoid this, and to make proper use of template tags, setup postdata. For this to work, you will need to use the $post global. Just remember to reset the $post global back to the main query’s $post value

foreach ( $items as $post ) {
    setup_postdata( $post );

    // Use normal template tags
    the_title();
    the_content();
    echo get_the_author_meta( 'ID' );
}
wp_reset_postdata(); // VERY VERY IMPORTANT