What the... I was under the impression that iCloud backups are end-to-end encrypted. This is a HUGE problem.
What did suck on Apple's part was that they wouldn't allow you to disconnect the actually end-to-end encrypted iMessages from the iCloud backups for many years.
So since most people kept their iCloud enabled, that meant their "iMessage end-to-end encryption" was nothing of the sort, as all messages had a copy that Apple could read on its servers.
I actually don't know if this is still true since I haven't used an iPhone in some time, but I sure hope it isn't anymore.