Is there a reason why my wordpress PHP page isn’t loading into my PHP template

I have not used ACF before but i suspect your post-2.php lacks $post_id as in have_rows($field_name, $post_id)(see). If you are using ajax there is no way that your ajax function know the page you are on and what post you are seeking so you better use $post_id to tell ajax function which post data you want.

Correct way of using ajax in wordpress is directing ajax request to ajaxurl = admin_url().'admin-ajax.php'. It is better to wp_localize_script but can do like this <div id="part2" data-url="<?php echo admin_url().'admin-ajax.php'; ?>"></div> and the ajaxurl = $('#part2').data('url);

You can use something like this

 $.ajax({
                url: ajaxurl,
                cache: false,

                type : 'post',
                data : {
                   action: 'load_post_acf' // This will be used in hook
                 },

                success: function(result){
                   $("#part2").html(result);
                   $('#loading-image').hide();
                },

           });

Ajax function for post-2.php you can do something like ..

add_action('wp_ajax_nopriv_load_post_acf','your_ajax_function');
add_action('wp_ajax_load_post_acf','your_ajax_function');

function your_ajax_function(){
  global $post;
  if( have_rows('repeat_field',$post->ID) ):
    // do something
  else:
   echo '<h4>No rows found.</h4>'; //do something else
  endif;


}