I thought iCloud Photos and iCloud Drive are a backup?

No. iCloud Photos and iCloud Drive sync your files. When you delete a photo or a damage happens on one device, the change reaches all your devices. Deleted photos stay in Recently Deleted for 30 days, then they are gone for good.

iCloud Backup doesn't cover them either: once iCloud Photos is on, Apple leaves your photos out of iCloud Backup (Apple Support). And with Optimize Storage turned on, your devices only keep small previews, so iCloud holds the only full-quality originals.

Parachute Backup keeps a separate copy of your originals on storage you control. Changes in iCloud never reach that copy unless you ask for it.