Why does thunderbird move the style of the html header?

I am creating responsive email templates, I use Thunderbird to send some tests.

In most email clients it works very well. However in Gmail the styles are not applied.

Checking the CSS support I found that gmail only supports <style> inside the <head> tag. MailChimp

Css Support in gmail

<html>
  <head>
    <style>
      .colored {
        color: blue;
      }
      #body {
        font-size: 14px;
      }
      @media screen and (min-width: 500px) {
        .colored {
          color:red;
        }
      }
    </style>
  </head>
  <body>
    <div id='body'>
      <p>Hi Pierce,</p>
      <p class='colored'>
        This text is blue if the window width is
        below 500px and red otherwise.
      </p>
      <p>Jerry</p>
    </div>
  </body>
</html>

Knowing this, I implanted my styles inside the head, however, the styles were not applied in GMAIL.

After researching on various forums and breaking my head I couldn't find the solution, so I checked the obvious, it turns out that Thunderbird moves the <style> from <head> to <body>

When I send the template through Thunderbird and see the source of the mail, I get this:

User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1

<html>
  <head>

    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
    <div id="body">
      <p>Hi Pierce,</p>
      <p class="colored"> This text is blue if the window width is below
        500px and red otherwise. </p>
      <p>Jerry</p>
    </div>
    <style>
      .colored {
        color: blue;
      }
      #body {
        font-size: 14px;
      }
      @media screen and (min-width: 500px) {
        .colored {
          color:red;
        }
      }
    </style>
  </body>
</html>

When I send the template through mailutils, the behavior is as expected and the styles work correctly in gmail

X-Mailer: mail (GNU Mailutils 3.7)

<html>
  <head>
    <style>
      .colored {
        color: blue;
      }
      #body {
        font-size: 14px;
      }
      @media screen and (min-width: 500px) {
        .colored {
          color:red;
        }
      }
    </style>
  </head>
  <body>
    <div id='body'>
      <p>Hi Pierce,</p>
      <p class='colored'>
        This text is blue if the window width is
        below 500px and red otherwise.
      </p>
      <p>Jerry</p>
    </div>
  </body>
</html>

View of gmail:

How to prevent thunderbird from moving the style to the body?
I am using Thunderbird 78.7.1, Ubuntu 20.04.2 LTS