Where did this Data folder come from?
If you have a backup, then go ahead and delete the folder. You are correct that it's not something Apple installs. Lots of third party database software like mongodb work best with a /data mount point - so if you can correlate the creation date on that folder with running an install script or package you might be able to infer which process created that folder.

There isn't an auditing system you can read to determine when or what installed a change generally - so use Finder to get information on the folder or perhaps try a tool like Pacifist to check receipts - maybe you will be lucky with a package claiming the creation of that /Data directory.