[dathinab]

> Why is it even possible to issue more than 1 certificate on the same domain via Let’s Encrypt?

it commonly used in a "normal" way all the time

- e.g. when there are multiple data-center for the same domain (e.g. using geo-location based routing) it's a good practice to give them different certs so that if you need to revoke one the operation in other regions is unaffected

- or when rolling over from on cert to another

- or when moving certs into hardware security keys/module (HSK) you preferably do have one per HSK (so that if e.g. hardware breaks and gets replaced you can just revoce the cert for the affected HSK module not all of them), you also normaly do not keep backups to make sure it can't be leaked at all (as long as the HSK isn't hacked which is normally quite hard)

- or losing access to a cert (e.g. in the case above a HSK breaks)

Lastly the whole CA system is in the end designed to provide good security for the industry while having the backdoor of issuing certs the legal organs to allow the police some degree of wiretapping (oversimplified, it's slightly more complex then that).