I lost my email completely even though it was backed up on iCloud. How do I get it back

The only email stored in iCloud is your iCloud.com email. No other emails data is backed up in an iCloud nor an iTunes backup. Emails have never been part of an iOS device backup.

If you re-install the email account, you should sync your emails back from the email provider’s servers.

15to wrote:

even though it was backed up in iCloud.

No it was not. iCloud backups do not include mail.

What does iCloud back up? - Apple Support

Perhaps your email provider still has your mail. Check their webmail site if they offer one.

Who is your email provider?

email is not backed up in iCloud. It's on your providers mail server.