Welcome to Android Central! Did you do the factory reset yourself, or did it seem to do a factory reset on its own as part of the Oreo update? If the latter, that sounds like a glitch, since a system update should never act like a factory reset.
SMS doesn't get backed up to your Google account -- saved messages are only saved locally to the phone, so a factory reset will wipe them. You need to use a 3rd party app like SMS Backup & Restore beforehand. Email accounts can always be added back to the email app, but if you were using a POP3 server and downloading copies of your emails to the phone (and deleting the copy on the server), then those also don't get backed up to your Google account, and would also be wiped with a factory reset. That's one reason why IMAP is a better idea than POP3 -- the emails remain on the server with IMAP unless you delete them there.