title: Beautiful Soup / urllib does not read some HTML tags
body: <p>I recently started using Beautiful Soup. For practice I'm trying to scrape <a href="https://www.countryflags.com/en" rel="nofollow noreferrer">this website</a>. </p>
  
  <p>There are some div tags that the scraper does not seem to be able to access, even the URL reader does not seem to read these div tags. The HTML does not indicate that it is using JavaScript for the part that is not being read, so theoretically I assume Selenium is not needed. Specifically div tags under an ID named "ajaxTarget" are the concern. The below code returns some elements, but the majority of the div tags under this specific tag are not read.</p>
  
  <pre class="lang-python prettyprint-override"><code>from urllib.request import Request, urlopen
  from bs4 import BeautifulSoup
  
  def main():
      url_link = 'https://www.countryflags.com/en/'
      req = Request(url_link, headers={'User-Agent': 'Mozilla/5.0'})
      page = urlopen(req).read()
      soup = BeautifulSoup(page, features='lxml')
      div_master_container = soup.findAll('div', attrs={'id': 'ajaxTarget'})
      print(len(div_master_container))
      for item in div_master_container:
          print(item)
  
  if __name__ == '__main__':
      main()
  </code></pre>
  
  <p>I would appreciate if someone can point out whether there is an element in HTML that I am missing or any other factor that is contributing to this issue.</p>