You created a specific page template for a page called ‘about’ but your page is called ‘About Us’. Try creating a page named ‘About’ or renaming your file to page-about-us.php.
Also use the cleaner formatting involving new lines:
<?php
/*
Template Name: Example Page
*/
get_header();
?>
You’re also not checking if there is a post and executing the loop regardless
if( have_posts()){
// put the while loop here
}
I have no idea why you have involved custom post types for this. You’re working with a page template, and you assign page templates to pages. Those custom post type definitions may even be interfering with the working of your pages if they have the same post type name as your pages slug.