Search XPath in PHP DOMXPath with Query function

Question

I have an DOMXPath object, that I created from a DOMDocument, that is this amazon website:

https://amazon.com/gp/aw/d/B0839N79CS

I am trying to use some XPaths that work on my Google Chrome, but when I try them on the DOMXPath they doesn't seem to be working.

Here is the example:

    $dom = new \DOMDocument();
    $dom->loadHTML($html);//HTML is amazon url
    $html_document= new \DOMXPath($dom);    
    $html_document->query('//*[@id="dp"]//*[@id="productTitle"]/text()');

If you check that XPath on Google Chrome inspector, you will see that it works and it gives you the product title. If I only put "//*[@id="productTitle"]/text()" it works, but the thing is I need to know why the other way does not work as sometimes I need that kind of XPath.

Thank you