As far as I know it was started by the original lemmy developers which made the software because they felt persecuted for their beliefs on normie social media. Lemmy just happened to be around when the reddit CEO decided to f up reddit so everyone started using it despite the creators not being well adjusted people.
There’s different kinds of backups. For this you don’t need off-site storage.
For this I set up zfs auto snapshotting which means when I delete stuff it isn’t really deleted because a snapshot is still pointing at it until it rolls off the time window.
Both zfs and btrfs can do this but you do need to change the filesystem to use these which can be a lot of work.