Encryption of the drive is not the issue. You could simply give someone else the license key and they could download the Windows software and use your key.
The problem is that the key gets tied to the computer it was originally installed on. When Windows is installed and you activate, it registers the key with Microsoft so it cannot be used again. Depending on the type of license, you may be able to reuse it on another machine, you have to contact Microsoft so they reactivate that key, assuming the license type will allow it. If it was an OEM install on the computer, then you cannot transfer. You indicate it was a full retail license you purchased, so it can transfer to a new PC.
These articles explain the steps:
https://www.groovypost.com/howto/transfer-windows-10-license-new-pc/
https://www.groovypost.com/howto/activate-windows-10-license-microsoft-support/