Wordpress - How to order posts of a custom post type by date DESC in dashboard Admin?

Alright, You can just hook into the filter pre_get_posts and check is_admin. Put this in your theme or plugin:

function wpse_81939_post_types_admin_order( $wp_query ) {
  if (is_admin()) {

    // Get the post type from the query
    $post_type = $wp_query->query['post_type'];

    if ( $post_type == 'Videos') {

      $wp_query->set('orderby', 'date');

      $wp_query->set('order', 'DESC');
    }
  }
}
add_filter('pre_get_posts', 'wpse_81939_post_types_admin_order');

I also would shange the post_type "Videos" to lowercase like "video".

The example above disables the ordering feature by clicking columns.

Sortable & for multiple custom post types:

function wpse_819391_post_types_admin_order( $wp_query ) {
  if ( is_admin() && !isset( $_GET['orderby'] ) ) {     
    // Get the post type from the query
    $post_type = $wp_query->query['post_type'];
    if ( in_array( $post_type, array('videos','news','text') ) ) {
      $wp_query->set('orderby', 'date');
      $wp_query->set('order', 'DESC');
    }
  }
}
add_filter('pre_get_posts', 'wpse_819391_post_types_admin_order');