iCloud drive deleted after formatting old macbook

Last week I bought a new Macbook, and did a complete transfer of my old Macbook Air (2017) to my new one (2024). I had acces to all my files like i was used to, on my new macbook.

This weekend I erased the hard drive of my old Macbook to sell it (Cmd + R while rebooting to reboot in recovery mode, and then erase all data). Before erasing I logged out of iCloud.

After erasing all the files were gone on all my iCloud devices (new macbook, iPhone, and www.icloud.com).

Is it possible formatting a hard drive deletes all this data, or is something else going on?

Is there a way to restore this? I tried several document recovery programs without result, best I could find were cache-files (like "%document", and if you click it it gives an error saying the file is deleted).

With google drive I know you can contact help center and they can recover files that are permanently removed, in an random order. Can the same be done for iCloud? There are in particular 3 word-documents with months of work (that I thought i had backupped in iCloud already, so it is the only copy...)

Thanks in advance for your ideas!