How does the Google Adsense advertising code work?

Question

JavaScript

Hello! I have a question, probably more technical. For Google Adsense, each ad unit looks something like this:

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<ins class="adsbygoogle"
         style="display:block"
         data-ad-format="autorelaxed"
         data-ad-client="ca-pub-1271381194193378"
         data-ad-slot="3961443235">
</ins>
<script>
  (adsbygoogle = window.adsbygoogle || []).push({});
</script>

I have such blocks, for example, on the page three. I decided to move the repeating code down before the closing tag </body>. Those. this part:

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<script>
  (adsbygoogle = window.adsbygoogle || []).push({});
</script>

But bad luck, only the first advertisement began to load.
After experimenting, I realized that the point is in this line (adsbygoogle = window.adsbygoogle || []).push({});, there should be as many of them as ad units. From here the question is whether it is possible to write like this, is it correct:

<script>
    (adsbygoogle = window.adsbygoogle || []).push({});
    (adsbygoogle = window.adsbygoogle || []).push({});
    (adsbygoogle = window.adsbygoogle || []).push({});
</script>

If we take a more global approach to the issue, then I want to somehow optimize the loading of blocks so that the pages load faster. Perhaps you can make the blocks load after loading the page content itself?