Platform Styles and CDN help

I can’t understand how Platform Styles work, in particular I tried to apply to an ionicv5 angular project with cordova

    <meta charset="utf-8">
    <script type='text/javascript' src="core/dist/ionic.js"></script>
    <link rel="stylesheet" href="core/css/ionic.bundle.css">

but the result is very different from

<script type="module" src=""></script>
<script nomodule src=""></script>
<link rel="stylesheet" href=""/>

Ionic Framework CDN seem to provide great layout help on mobile platforms, can anyone give me some clarification?

thanks in advance,