Judging by the errors in the console...
Uncaught SyntaxError: Unexpected token < /v2/wordpress/wp-content/plugins/lightview-plus/js/spinners/spinners.js/?ver=3.1.0:1
Uncaught SyntaxError: Unexpected token < /v2/wordpress/wp-content/plugins/lightview-plus/js/lightview/lightview.js/?ver=3.1.0:1
...it looks like these two scripts being referenced in the code are missing or have incorrect paths:
<script type='text/javascript' src='http://www.mattemig.net/v2/wordpress/wp-content/plugins/lightview-plus/js/spinners/spinners.js?ver=3.1.0'></script>
<script type='text/javascript' src='http://www.mattemig.net/v2/wordpress/wp-content/plugins/lightview-plus/js/lightview/lightview.js?ver=3.1.0'></script>
The source code says the youtube video is supposed to be played inside a Lightview. If the js can't put it in one, that would make sense why it's being embedded full screen.