Remember, "root" and "intermediate" are terms that apply to certificates, not organizations. Let's Encrypt does operate two root certificates which you can see

Remember, "root" and "intermediate" are terms that apply to certificates, not organizations. Let's Encrypt does operate two root certificates which you can see installed in your OS/browser. They also operate several intermediate certificates (which were issued by their root certificates), since CAs are not allowed to issue website certificates directly from roots. Root and intermediate certificates are both able to issue further certificates; the difference is that roots are installed directly in your OS/browser.