unlayer the html exported seems styleless when viewed

Question

I am trying to export the HTML of a template to try and see if I can send an email that looks exactly like the template, however it seems I am missing something as the results looks styleless.

Here is the template example I am trying to extract the HTML from :

and here is the result in an online template viewer :

Is not everything in the data.html from the response of extractHTML? What am I missing here?