When it comes to dealing with a hacked website, one of the recommended solutions is to revert the website to a clean backup. There are multiple possible issues with that, including not knowing whether a backup is clean or not, as well as that reverting to a backup doesn’t resolve the underlying issue that caused the hack in the first place.
Another problem we noticed while dealing with a recent clean up of a hacked WordPress website is that backup plugins for WordPress don’t necessarily backup of all the website if there is content that isn’t handled through WordPress. While that makes sense from the perspective of the backup plugin, it is something that is necessarily going to be thought by those using them, until they run into a problem that requires the backup.
Whether that situation applies to your website or not, it is a good idea to check to make sure that backups being made are complete, as you can also run into issues with backups being incomplete for other reasons.