You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <revisions rvcontinue="516" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Admin" timestamp="2017-05-15T10:37:59Z" comment="Link to new LPWAN Security page" />
          <rev user="Admin" timestamp="2015-05-02T13:09:43Z" comment="Banner for new article" />
          <rev user="Admin" timestamp="2012-05-18T16:17:54Z" comment="/* Welcome to the Franklin Heath Ltd Wiki */ Link to the Enigma contents page rather than listing the contents" />
          <rev user="Admin" timestamp="2012-02-03T00:25:55Z" comment="Added index of Enigma pages" />
          <rev user="Admin" timestamp="2011-11-05T23:40:45Z" comment="Protected &quot;[[Main Page]]&quot; ([edit=sysop] (indefinite) [move=sysop] (indefinite))" />
        </revisions>
      </page>
    </pages>
  </query>
</api>